My girls seem to prefer the take n toss or playskool sippies with the wider mouth (hate the playtex ones). The tops don't screw on though - should I try and get them onto a sippy cup with a screw on lid? I have visions of them walking around with sippies and throwing them against the wall and milk everywhere!
Also, how many did you need?
Re: Sippies
I think if they like a certain type, go with it. They'll find a way to spill milk everywhere regardless of the type you have anyway. But I really don't know, my girls have liked the screw on ones.
We have enough sippies to get through the day only washing them once. That means 10 for us (one for each meal, one before bed and one that is out with water most of the day), but the exact number would depend on your schedule.