XP in DF Felltower is run off of a "loot threshold" method that I detailed in DF21. I allow unequal splits of loot to allow people to meet that threshold.
The tier we use is "Method 3" - 100 points, then 50 point tiers, like so:
Required Profit (Tiered, 100, then 50 point spread)
Up to 249 Points: $100 each (1/5 Struggling)
250-349 Points: $200 each (1/5 Average)
350-399 Points: $400 each (1/5 Comfortable)
400-449 Points: $1000 each (1/5 Wealthy)
450-499 Points: $4000 (1/5 Very Wealthy)
500+ Points: $20,000 each (1/5 of Filthy Rich)
Every Additional 100 Points: x10
I may at some point switch to a full "Method 2" loot threshold, which cuts the first tier from 250-349 to 250-299 and moves the rest down appropriately.
One reason is because 300-349 point guys taking $200 for 4 xp is feeling lame, especially after having made two full passes through my dungeons revising treasure up substantially (the system in DF21 reflects this revision.) A 300 point character is substantially more powerful than a 250 point character. It's also 10 successful delves worth of trips, yet to still only need $200 (when $150 pays for upkeep) seems weak. You could potentially go from 250 to 350 points in 20 delves taking in a grand total of $4000. You're better off bottom feeding on the lower-return treasures for your first 20 delves, just trying to make enough to get by, than to take any real risks.
Plus, the 349 to 350 jump is a big deal, as it doubles your required return. Players can and do save up for something big so that jump is not just "1 more spell" or "Learn Survival (Woodlands)" or something, but rather "+1 DX" or "Extra Attack" or "buy Weapon Master." (Admittedly, dropping this to 299 to 300 jump might do the same earlier . . . but the stakes are necessarily smaller.) This isn't a problem, but it is a thing.
Also I think it makes people with less than 350 point character think of themselves as newbies. I've heard a lot of "we're delving pretty deep for our point level" type of comments - although not in so many words - as people delve on levels and in areas originally set up with 250-300 point guys in mind with 350-450 point characters. I've seen decisions made based on trying to get XP from minimized risk. It's appropriate behavior given the incentives, but it does mean we've played DF Felltower for over 9 years and I can count sessions spent below "level 4" of the dungeon on one hand. The number of gates really, truely braved is limited, too - and the vast majority of gate travel has been to one gate, leading to an area of known, moderate risk - the Lost City. Any gate with some actual danger has only been visited ones (Olympus, Icy Gate, Forest Gate, Air Gate) or zero times (all the rest except the Ape Gate.) Why? It doesn't really take that much loot . . . and if you feel fragile, you'll act fragile.
Another reason are uneven splits.
In DF Felltower the split get handled in a very game-y, self-aware fashion. Galen doesn't get 3 shares, or 4 shares, or something, he gets $4000 on the nose if it's possible to get him $4000, or he gets $800 + extra if there is extra after the others get $200 or 400, etc. It's very meticulously plotted out. I don't really care, but as a flavor thing, it's a downside of my approach to keep in mind if you allow unequal splits!
The main issue I see is that this encourages the powerful gusy to "bottom feed." You don't really need that much money to get 2 xp or 4 xp. You can basically take a 450 point guy (4K or 8K) and a 400 point guy (1000 or 200) along with 8 250-349 point guys (200 or 40) on a delve and only need $6,600 for max XP for everyone or $1320 for 2 xp for everyone. $1320 is 5 opponents with thrusting broadswords sold at 40%. It's not a lot. It's not even enough for upkeep for the whole group ($1500).
You get the oddity of guys with Greed arguing to unevenly split the loot away from them so the skilled guys get more XP, because it's the smart move and allows them to make more and more in the future. It's a bizarre artifact of the system. The players get put in a bind where staying in character is pushed against by the needs of a better, more gamist positive result.
Unequal splits of money in a gold-for-xp system like older D&D systems encouraged given the big loot to the lower level guys so they'd learn faster. At least this approach encourages paying the high-end talent more in order to get everyone the win. That's a very serious upside to allowing this! It doesn't always work that way, though. If the whole group is falling short, the loot split tends to reverse - the big guys get 0, and take 0, and give all of the rest to the others to get as many people as possible as much XP as possible.
Although it hasn't happened so far due to the personalities and needs of the top-point guys in DF Felltower, soon enough a generous type will be the rich, high-point delver. They'll happily take the $4000+ for full points (450-499) or 2 xp (500+) and then spend it on gear for their buddies. So it's pass the money up for xp, then pass it back down for gear. Double-dipping at its finest. You get the XP from the money split unequally - and everyone benefits - and then you use the money euqally - and everyone benefits.
The only way to solve that, I think, is allowing unequal splits of loot but assigning XP by the total loot taken divided evenly.
That might also be an interesting way to deal with the "bottom feeding" issue. If you really need $20,000 x number of PCs to get the 500+ point guys 4 xp for treasure, it doesn't matter how many orcs you whack skulking around level 2 and "pruning the orc tree." With 8 players you'd need $160,000 to make it worth the big guy's while, and $32,000 to earn any XP at all.
Putting in both of the rules would be a very abrupt change in how things are done. Putting in one or the other might not deal with the behaviors. I have in the distant past put in fairly parsimonious treasure. I went back through Felltower in multiple sweeps raising the loot to higher levels (which are reflected in DF21 and the random treasure system there.) So more money is there, and has been for a while. Even a single-fight delve against a mid-level boss monster and a handful of minions (such as our most recent session) generated enough for everyone to get max XP. The high-point characters weren't in any real danger, and the lower-point characters were threatened (hey, it's a boss encounter) but not especially so. It's not terribly hard to pull down a fair amount of loot anymore, if you go where it is instead of exploring where it used to be. But the XP system encourages hunting orcs for swords and skimming off loot and piling it on higher-point delvers as needed.
I'm undecided if I'll do one (change to Method 2, the only one seen in DF21 or banning unequal splits for XP purposes) or both. They might need to be done together, to encourage the risk/reward drive to push actually quite powerful delvers to take something more than minimal risks!