Just ordered an M&P 15-22. Shot a guy's this weekend, and it's an awesome lil' rifle. I want to get the quietest can for it. The can will pretty much live on this rifle. I'll eventually gets threaded .22 pistol, but will still do nearly all the shooting with the can on the rifle. So, rifle performance is king. I'm considering the following. Let me know which is best, and don't hesitate to throw out a suggestion.
AAC Prodigy (hear that the rifle performance is awesome, but that FRP is meh)
AAC Element II (this seems more like a pistol can, and is way pricey...for me)
SWR Warlock II (cheaper and lighter than the Spectre II, I'm only shooting .22, so I don't need the Spectre, heard they both perform the same on .22)
Gemtech Outback IID (heard this is the best bang for the buck on size, went and performance...I'm concerned it won't be as quiet as others)