I prefer Snupin as well. Lupin is one of the few people unruffled by Snape's behavior.

I tried a couple of summers ago to write a fanfic that started out at the end of GoF, when Sirius was sent "to go lie low at Lupin's". I could never quite get the hang of Sirius. He's an incredibly difficult character to write and I've read too many puppy-ship stories that get the dynamic wrong.