I have the Colt and an Engage/BCM/Noveske mutt. Both are great. For you I would go with the Colt.
There has been some debate on the legality of the M&P15 (even the sport), and I would rather play it safe. I prefer the Colt anyways so I guess it's just a bonus. Buy once cry once.
Edit: if you're at engage, check out some piston AR's. They have a different mechanism so they aren't technically AR15s if I recall correctly. I'm tempted to buy the FDE Sig even though I just finished a build. Awesome folks there too. Can't go wrong at engage.
There has been some debate on the legality of the M&P15 (even the sport), and I would rather play it safe. I prefer the Colt anyways so I guess it's just a bonus. Buy once cry once.
Edit: if you're at engage, check out some piston AR's. They have a different mechanism so they aren't technically AR15s if I recall correctly. I'm tempted to buy the FDE Sig even though I just finished a build. Awesome folks there too. Can't go wrong at engage.