I don't really like either, but I don't like any of the wolves in acnl, their design isn't very pretty to me.
And although I don't like any of the existing sheep, I simply love that they're so tiny and fluffy. It's very cute!
I'd like the wolves a lot more if their personalities were more varied and their designs were different.They all have the same pointy fur and big mouths and there's like 42 cranky wolves,19 snooty wolves but no peppy or lazy wolves.They even changed Dobie from a lazy to a cranky for the Amiibo update.I like just about all the sheep except for that one that looks like an eggplant with a face.Yeah,I voted for sheep.Baa.(humbug)
Seeing as my favorite villager is a wolf, and I like more wolves than sheep...definitely wolves for me! I like a good number of the sheep but I have bad memories with two in particular so that's kind of tarnished their reputation in my mind. Still a better species than the frogs IMO