you wouldn't notice the difference. this is all behind the scenes.

ok you would notice it if you tried to delete one of your cards. because in nostr you kinda can't, pubky you kinda can.

or if you wanted to see exactly how many followers someone has (again nostr you kinda can't, pubky you kinda can).

but only for specific actions like that. the general sense of being in a twitter-ish world would be the same.