>>51670060USUM is such a weird case, while third version like Emerald and Platinum are clearly the same game but upgraded, and while B2W2 are clearly new game but using the original as a foundation, USUM is right in the middle.
it's clearly just an upper version, but there's still many differences, like added content to the main story, character being used in a total different way, heck there's even new pokemons and new forms.
but it's so weird, they feel and play like different pokemon but they are still way too similar, I can't decided and tell if you just play SM (the better version) or play both SM and USUM since they feel different..