I want to convert from V-Brakes to Disc Brakes. I have a Motobecane Cafe Sprint (Hybrid) that I use for everyday commuting. I want to use Shimano Deore XT brakes but I'm not sure which rotor size would be best for commuting or if the size makes a dif. This will be my first set of disc breaks...Can someone help me out and let me know how size makes a dif for bike rotors? My choices are 160mm, 180mm and 203mm. I can't wait to get some advice...Thanks.