man oh man. great arguments you could make either way
Eminem has lyrically slaughtered every rapper who's ever dared cross him, but that long list includes a bunch of corny rappers who have had no business arguing with Em in the first place (Benzino, ICP, MGK, etc. etc.). So those victories are a little less impressive.
Tupac had a shorter career (no fault of his own: his life was taken way too soon), but he went toe-to-toe with Biggie, one of the undisputed GOATs, and came out on top of that rap beef IMO so
More than likely, they would have just respected and avoided each other, because real recognize real and it would have led to mutually assured destruction lol.