I voted pins, but in all fairness I only HAD pins 14.5 years ago when I was CDing a newborn (for a variety of reasons, DD2 and DS weren't CDed until they were bigger babies.)
I'm not sure if snappis existed 11-14 years ago (when I was CDing my daughters) or not, but I didn't have access to them if they did. I read about them when DS was a baby, but had no interest in trying them since I was already comfortable with diaper pins, and anyway I had a lot of fun sewing different kinds of velcro covers, side snapping fitteds, etc.