Are you using a KIU or AW (soft start) socket? If so, the cammed reflectors won't fit on mine, unless you remove the portion that makes it a "cammed" reflector. If you are using a FM ceramic holder, I haven't had any problems at all using a cammed reflector.
The differences between the cammed and camless is of course, the cammed will allow you to turn the reflector head to switch from spot to wide; similar to the stock maglite. FiveMega's cammed reflectors are nice in that you can remove the bottom portion, and make it a camless reflector. Whichever one you order, make sure it can fit the slightly wider ROP Hi bulb (wider than the WA1111). If you ever decide to go the Philips 5761 route, then you will need the even wider opening reflector that FiveMega also sells.