All Kleenex are tissues, but not all tissues are kleenex. All thumbs are fingers, but... well you get the idea on the Colt/AR-15 thing.
I just picked up an LE6920 from Colt, and so far love it to death... cheap PMC .223 plinking ammo, and it shoots like a dream from 25 to 225 yards so far.
You didn't mention your price range, but my Colt was about 1000-1100. And one of the joys of this weapon platform is that you can always find something new to swap in and out, and back for what was there in the first place. They're like Legos. You can have a lot of fun taking them apart and putting them back together differently. So, with that said, if I were you, I'd buy the best base model I could.. Preferably Colt(for me), for both the quality and the name at a reasonable (for the quality and name) price... And then start tinkering. Another brand name that puts out quality comparable to Colt as far as durability, twist, barrel lining, and so on is Noveske. They also seem to charge a little more.
Daniel Defense, I've heard good things about, but haven't checked them out much, beyond their two part freefloat handguard drop in upgrade that I'm still on the fence about. Quad Rails makes it too easy to turn your handguard into a batman belt, though extending the top rail would be nice for optics mounting.