I like my Armalites.
That being said, Bushmaster makes a nice gun. Wilson really
is overpriced.
If this is your first AR, or your first semi-auto rifle, I'd suggest going with a Bushmaster, DPMS, Armalite, or Rock River. They are commonly available and they're easy vendors to work with in case they managed to screw smething up. They're also good rifles and you don't have to give up your frst born.
Length of the barrel doesn't matter for what I think you're trying to do (plinking, shooting paper, having fun)... there's some gain with a 20" as opposed to a 16", but if you're going to get into competitive shooting, you'll probably be getting a 24" upper anyway. I prefer 20" barrel set-ups simply because of the longer sight picture. Bushmaster makes a carbine variant (Dissipator) with the 20" furniture, however, if you're wanting to go down that road.
Stick to USGI magazines. The pretty black plastic magazines look tempting, whispering "buy me, buy me," but they can be a pain to work with. The only time I have ever had feeding problems with my Armalites have been when using Thermold magazines. Orlites aren't any better.
However, about the new Bushmaster with the faux collapsable stock... I'm sorry, I just think it's goofy to have a collapsable stock that doesn't collapse. As GGGLOCK noted, you cannot even get a good cheek weld with it. I could see getting a pre-ban with a stock that collapses, because there's some utility in the collapsing stock. But the pinned stocks are only good for getting people at the range to go googoogaga and say, "can I touch it, can I touch it," but beyond that...
(if you really want to compensate for manly shortcomings, go get a Desert Eagle in .50AE)