Rant spoiler-ed below, because its mostly just complaining, but it feels like a lot of games lately have added 'gamified xp' to their systems, and I don't understand the appeal at all. The most positive any player I've talked to has felt about the systems are 'meh, I could take it or leave it', with most slightly disliking them.
So, mostly, I'm looking for people that like these kinds of mechanics (I have to assume they're out there if so many games feel like they're adding them), and what you is it you like about them.
But I feel like Milestone XP just makes the most sense for any traditional coop party RPG.
rant
I like trying out a bunch of different systems, and there's a lot to like, especially with a lot of the smaller games out there. I do like there 'narrative' approach ttrpgs feel like they've been taking recently, but between Chronicles of Darkness, ICON, Forged in the Dark, Apocalypse world, etc., and all there spinoff systems all having XP be earned for specific actions in game, its just a pain in the ass, that takes me out of the action.
I mostly GM, but I strongly prefer milestone XP. For some of the above games, its easy enough to gut their bespoke XP systems out of it, and just have players advance over time, but in several of them, it fucks with the overall balance, since several actions are 'bad', but made worthwhile because they earn XP.
But I don't like the feeling of interrupting game to award point, and adjudicate character advancement. And I hate systems that have players advance unevenly. There's always going to be a certain degree on uneven-ness in player attention, of rules mastery, and of spotlighting. As GM, its important to manage those so that everyone gets a chance to shine. But it just feels like increasing that workload for the GM, to need to additionally pay attention to the XP, and try to drag or XP share the players that don't find those systems engaging to not mechanically fall behind.
And as a player, I tend to have higher system mastery and attention than the others I play with, and tbh it feels bad to end up with more XP because of that. But also, it feels bad to knowingly pass up free XP by purposefully not engaging with those systems.
Really, only Call of Cthulhu and Paranoia feel like their gamified XP fits, and that's largely because the games are supposed to feel hopeless and unfair, and in the case of Paranoia, gamified and playing favorites.
I like the way the gamified XP in Flying Circus works. It's a game where the players are all old-timey fighter pilots in like an alternate fantasy world. You earn XP by removing stress from your character, and the gameplay loops is that you basically go up into the air to risk your life (which is a very stressful endeavour for your characters), and then you land and go drink and do drugs about it. I still haven't played enough to have a super good opinion on how good it is but I think it does a good job of making optimal play also the most narratively interesting play, which is IMO a good way to do things.