I have been using a TM and a UTG shotty for awhile and love em. Tho tough to use outdoor indoor they are a blast. The M500 gas ones are nice as well, but when they go down its a pain in the butt to fix if your not a technical guy like me. Plus I hate how its not very easy to reload in the middle of a firefight.
Plus they are usually more expensive and if you have the 8mm version they can HURT allot if you shoot someone too close.