I've been firmly in the "Bless you" camp for years now. There were a couple of years after taking Spanish language classes when I toyed with "Salud", but it's been strictly "Bless you" after sneezes for most of my life. It's my culture and heritage. I don't actually believe any silly sneezing superstitions, it's just a reflex. Hear achoo, say "Bless you." That's how it goes.
Mike has always been a Gesundheit-er. He argues that it is more fun to say and he is certainly not wrong there. I could never get into it. To me, it kinda sounds like you are making fun of the way the person sneezed.
The Bumble, meanwhile, mostly ignores sneezes. At least, she did until last week. Last week, I sneezed while driving and this little tiny pipsqueak voice piped up from the backseat, "Zoon tite!" And every sneeze since then has been met with an enthusiastic "Zoon tite!" So, Mike wins this one.