guess i'm late on this one, but i own a m & p sport.
i'm not very knowledgeable about AR's, but i wasn't gonna spend a lot more than i spent ($679), considering i was never a super fan of AR's. but i got the itch, and i got the sport. sometimes they can be had closer to $6-650....deals better than that are rare, in fact....i have never seen them. i think many claiming to get them for $600 are not adding ffl, checks, shipping, etc.
idk about all the specifics, but i have put close to 500 rounds through mine without a a single problem so far. i have put together close to 1" groups with a cheap red dot at 50 yards and just OK ammo, making me believe it may be a
1-2" shooter out of box with good ammo and a scope.
imo most people with AR's are just using them to plink, hunt, or punch paper....not go to war or anything....so i think you'll be super happy with the sport if this would be your primary uses for it. i personally can't understand spending much more for a gun to plink or play around with. but i am a well known cheapo!
just my 2 cents....i'm a happy sport customer!