Well we don’t know what those features are yet, otherwise people would already be trying to implement them! It could be anything though, maybe the servers are just much faster, maybe the UI is more slick, maybe they’re the first to implement a load of the features we like from RES, maybe they sell you some extra content for that vendor lock-in. Whatever it is, if they implement it in an unfriendly and/or incompatible way, they start a schism with the rest of the Fediverse; if they’re sneaky and wait until they’ve already got their claws in before doing this then they take a chunk of the more casual users with them.
All this isn’t guaranteed to happen, but it seems relatively likely and therefore something people should be prepared to deal with!