I've been on the men's Terry Zero for a couple years now. I love it!! And they now have a womens version, too. For me the cutout is they key. The zero is less bulky than the butterfly.

I have the men's Fly on the tandem I ride with DD. I prefer the zero. (But my fly is the blue one that matches DD's blue butterfly, so I can't swap it out or the tandem wouldn't look cool! Plus, we're not doing any centuries just yet....)