It's interesting to me how conversations about specific topics sometimes crop up in multiple unconnected places at the same time. Just as Ryan Macklin is discussing disadvantages and experience points in his blog, there's also a lively exchange on experience points going on in Google Plus. The G+ conversation is, unsurprisingly, more focused on XP in LARP design, but I think the conversations inform each other in interesting ways. There's a lot going on here, and that G+ conversation isn't readily available to most of my readers, so I'll recap. Um, this is going to be long. Go get yourself a frosty beverage.
Ryan Macklin examines the evolution of disadvantages over the past 20+ years of game design, starting with extra character points only at character creation (Old WoD, GURPS, D&D 2e Skills & Powers, etc.), continuing through disadvantages granting XP whenever they hinder the character during play (New WoD, probably a bunch of others), and ending with disadvantages granting Plot Currency rather than XP whenever they hinder the character during play (New WoD's Virtues and Vices, FATE's Aspects, etc.). In the comments, though, he asserts that the broader gaming community is just fine with characters advancing at different rates. I find this to be simply false, but neither Macklin nor I truly have anything beyond anecdotes. On the other hand, this is my blog, and I'm comfortable laying out why I object to characters receiving differing amounts of XP.
And Now for a Ton of Exposition
The games I cut my teeth on were D&D 2e for tabletop and Shattered Isles for live-action. As many readers will recall, 2e had differing XP charts by class, and had optional rules for each class receiving XP for different things (the fighter gets XP for defeating monsters, the thief gets XP for amassing filthy lucre, and so on). Self-taught DM that I was, I didn't use those optional rules, but I did grant small amounts of bonus XP to individual characters for good roleplaying, successfully doing awesome things, and so on. I don't think players cared a lot one way or the other back then, but it's not something I'd do now. Nowadays, I'm much more aware that some players are more vocal, assertive, and motivated than others, and the game absolutely doesn't need to reward them with more character power on top of that.
In fact, I am currently involved in one game that tracks XP separately for each character (Arcana Evolved), and still clearly remember the Pendragon game we played for around three years that awarded separate Glory totals for each character. In AE as in 3.x, enchanting magic items is a cost borne solely by the enchanter (exactly one member of our party), the standard level-loss-for-death rules are in place, and the DM grants bonus XP (equal to 50 x average party level) to each player who completes a journal or similar content-creation work since the previous session. Further, new characters come in at the minimum number of XP required to be of the same level as the lowest-level member of the party. The balance to all of this is that, as in standard 3.x rules, lower-level characters earn more XP than higher-level characters in a party of mixed levels, so it's theoretically possible for lower-level characters to catch up. With all of that, there's just one more complicating factor: some classes must perform ceremonies to increase in level, which means that some players have gone for multiple sessions without gaining the level they have earned (and thus continuing to earn XP at the better rate of the lower level).
This is kind of complicated bookkeeping, with lots of checking and re-checking that the players' records of their XP totals and the DM's records of their XP totals agree. It's fine that it works that way... mostly because I'm not DMing this campaign. This system doesn't cause hard feelings, in part because the DM isn't making value judgments in awarding XP. It's still far more spreadsheet maintenance than I would care to do, were I the DM.
Then there's Pendragon and its Glory system. The short version is that it's a bizarre mess that strongly encourages powergaming and point-grubbing. Glory (the system's XP) comes from a wide variety of sources, from defeating opponents in combat to maintaining spiritual purity appropriate to the chivalric code and your character's religious beliefs. Glory totals vary wildly from character to character, including bonus starting Glory if your new character is eligible to inherit 10% of the Glory of a retiring character (which has the ultimate effect that experienced players who know the system well keep a healthy and expanding lead over new and inexperienced players). Glory can improve your combat abilities (improving your ability to earn Glory) or personality traits (granting yearly Glory for high Virtues or Vices, and granting yearly Glory for religious bonuses, and granting yearly Glory for being chivalrous - the latter two also improve your combat abilities) or ability scores (granting strength in combat and yearly Glory) or Passions (granting yearly Glory for high Passions, which can also help you in combat - but don't bother using Passions with low scores). Just to be clear, "yearly" in this case means "at the end of most sessions."
But that's not all. Most treasure in the game comes from loot in combat, though if you're lucky your manor may produce wealth rather than being a sinkhole. Having more manors sharply increases the chances that you will make money, since costs are nearly a fixed value. Spending money on your personal upkeep (clothing, food, etc.), owning manors, and building new upgrades to your manors all grant Glory for conspicuous consumption. All of this together means that in every aspect of the Glory system, the rich get richer as the poor fall further behind. Bitter commentary on real life? Sure. Good for the game? Not so much. It comes across as awfully punitive, especially for characters who try to play even slightly outside of the game's central archetype of the chivalrous Christian knight.
In addition to the complex Glory system, there are two other systems for improving statistics that offer a limited degree of room for lower-powered characters to catch up. Characters can either gain d6 points (our GM included "reroll all 1s") to add to skills (only) below 15, or can add one point to any personality trait, ability score, skill 15 or above, or Passion. Further, any time you roll a critical result in combat, and any time the GM feels generous, you place a check mark next to a skill, personality trait, or Passion. At the end of every game year, you roll a d20 against all checked attributes, and gain one point in that attribute if you roll equal to or greater than its current value. Obviously this makes it harder for high values to increase, so it very slightly mitigates the rich-get-richer situation.
One of the really interesting things that's going on here - and the source of all that point-grubbing that I was talking about - is how much control the player has (at least in theory) over how much Glory his character earns in a year. Completely aside from choices made in combat, the player's decisions about increasing stats and spending character wealth make a substantive difference to the character's future income of those same currencies. Player-directed XP gain, even if it's only part of your overall XP, is something that comes and goes in game design. One notable recent appearance, as mentioned in the comments of Macklin's post, is Dungeon World.
There are still more examples to work through, so I'll move on to Shattered Isles. When I started playing SI in 1998, players received a "blanket" (absolute minimum) of 4 XP each event. After the conclusion of a module, and again on Sunday morning, staff members handed out XP chits to people they had noticed during the event. XP chits ranged from quarter-XP to 1-XP chits, and if you passed the cap (10) I'm pretty sure you could save them for future events. You could also spend Brownie (volunteering credit) to reach the cap. This system continued until sometime around mid-to-late '99. Rehashing the problems with that incarnation of the system seems mostly unnecessary; I will keep it brief and say that even the best staff members likely found it difficult to stifle a kind of instinctive favoritism. People who were unlucky enough or shy enough not to get involved in stuff also didn't get much in the way of XP, so they didn't gain much power... which meant they'd have a harder time getting involved in the future. The staff members didn't really get to know me until I'd been playing for a year or so; SI had a big playerbase in those days, with a lot of churn, and (shy as I was) I found it very hard to get to know the staff members and higher-profile players.
The system they adopted in its place is nearly identical to what we use now. Players receive a blanket of 7 XP, and receive additional XP (up to the cap of 10) when other players and staff members vote for them in their feedback forms. This system has issues of its own, but as more votes go into the system than the number required for everyone to reach the cap, it can be safely said that people almost never fall short. There's a feeling, though, that people have to vote for their friends so that their friends will cap. This is a problem because, while it is rational behavior on the part of players who want to support their teams, it fails to address Plot's goal for having XP votes in the first place, which is to hear about how players are being awesome and making other players' events better.
In Which I Get to the Point
So I'm really addressing two separate points in this post. The first is that players within a tabletop game or a LARP advancing at different rates from one another isn't really useful, and especially in tabletop games leads to bookkeeping pressure without much in the way of payoff. Even though everyone in my games (D&D, Mage, Over the Edge) receives the same XP total for ease of bookkeeping, I continue to use XP totals (rather than just telling players when they advance) for a few reasons. Primarily, I want to reward sessions with more player engagement, danger, and plot advancement with a larger number. Secondly, I think (without a lot of evidence, admittedly) that players do feel a certain reward in watching conceptual bars fill up. Mage in particular has issues of tradeoffs and granularity, as I've discussed; also I don't really want to change things up mid-campaign. Were I to start a new Mage chronicle, I might give more consideration to different advancement systems - perhaps with an eye toward more actively opaque ones, just to reduce player focus on not quite reaching that new dot of their Ruling Realm just before the big showdown.
The second point, which grows out of the first, is that I don't find much joy in the point-grubbing of disadvantages, as players look for low-hanging fruit. In combination with disliking uneven advancement and playing a lot of games that don't have a clear Plot Currency/Fate Point system, I'm more interested in some other system of disadvantages. Right now, my favorite is the one used in Over the Edge, which requires that each character have a flaw. Players don't get anything for having that flaw, and the example flaws range from things that look like low-hanging fruit (that the GM is encouraged to screw them on) to things that look obviously terrible. When asked to make up a flaw for themselves, though, my players provided me with excellent material.
An alternative method I was thinking about is making the payoff for flaws not XP or Plot Currency, but points used to build whatever the party's cooperative thing is (sanctum, airship, noble house... you know the drill). I feel like the mental process of "I'm taking on this Bad Stuff so that we'll all have more fun with our group resource" is exactly the way you want your players thinking at the start of a game. It might also make it easier for players to be patient when someone else's flaw is an inconvenience for the whole party.