>>55410840There's more Pokemon, few more things to do, certain location-based evolutions can be done bit earlier, the initial few minutes of the game have better pacing and there's more post-game content. The only gameplay-wise bad things in USUM is Rotom dex that will not shut the fuck up, especially if you allow it to give you a nickname and arguablly
the U-Necrozma boss fight being way over the top in terms of power.
Story wise it's just forces a lot of weird shit involving aliens that never do anything relevant and turns the main villain into more of a shitty anti-hero. Also changes a bit focus on characters - Lillie is slightly less relevant and Hau gets more fleshed out (but still he fucking sucks). And the post-game quest is bunch of nostalgia pandering that may or may not be amusing, depending on how much you enjoyed [spoilers]villains from previous gens.
Generally it's still very similar game but there's bit of changes sprinkled around. Hard to tell which is better.