The pointers and weis are a bit bigger than collies, but the vizslas seem to vary a bit, ours is quite small, certainly no bigger than a collie, but I've seen them quite a bit bigger too. On the subject of size, I met a woman with a MASSIVE great dane at the part a couple of months ago, it was enormous, and she said they're actually popular dogs for apartment dwellers as despite their size they're really lazy!
I think the collie would be a great dog for your situation, good luck trying to keep it as an outside only dog...