Well, yes there's the sync issue. I don't use flash that much but it would be handy. I shot a wedding* for a friend with the pentax a few weeks back with the pentax.
Anyway, I've been shooting with the bronica Sq and I find myself switching films while on the same setup while the camera is on the tripod. I like having the option to change it up like I do when shooting large format. This would be a pain to do with two separate Pentax bodies.
I also like the fact that I can do several hour exposures with the Bronica system and not have to worry about the shutter closing due to dead batteries.
I may just sell the SQ system, get a small GS-1 kit and try it out.
*I've shot a few and every time I swear it'll be my last.