What size should I get. Ugh.

After my front fender recently got banged up (thanks, shitty LBS!) and I need to get new ones. No rush, since my other two bikes have them and can take on raniy-day-duty in the mean time.

I want pink so that pretty much means I need soma. But what size? Apparently my bike can take either hybrid 45" or road 37", I'm running 28" tires, I think 700C (how do you even tell? It also says "32" on the tire, IDK)

Bigger fender for more clearance if I want bigger tires later? Or smaller fenders for a better looking ride? Will the smaller fenders fit for sure? Any other reasons? I'll probably never need bigger tires, do the smaller fenders really look that much better? I need advice : /

http://www.somafab.com/accessories/fenders
the bike in question is the black soma in my signature.