First off what are your goals for this rifle?
The AR can be anything you want. Want a precision shooter 1/2 moa 100 yards. No problem. Want a police carbine, short carbine, M4 copy etc. All good. Or a mix of the two. Decide what's important to you. There are tradeoffs.
You were saying a 16" barrel. Ok, now you need to figure out what is important to you and what is available. First do you want the M4 profile barrel? Do you want the regular front sight with plastic handguards, or do you want to go free floated rails (I would recommend free floated). Then there is the case of the Monolithic uppers. All one piece and free floated. LMT offers this with their MRP line.
Now one other thing to be careful of. Look what the rifle comes with. Sometimes it's cheaper to buy the more expensive rifle if it comes with the pieces you already want, than the cheaper one and having to add on later.
Stock choices. Magpul, CTR for patrol carbine, PRS or UBR for more DM rifles. Also the SOPMOD stock by LMT while expensive on it's own works very well. Others have found Magpul comparable. The FAB defence stock I have on a patrol carbine is decent too.
Pistol grips: Magpul MIAD, or MOE. Now that being said the Ergo grip that came with my LMT won't be replaced. I actually really like it, although my others all have Magpul.
Triggers. The triggers on AR rifles vary. Some are great out of the box others are complete garbage. Again another thing to consider in the overall price.
Sabre is supposed to be good. LMT MRP if you want to go up a level is also excellent if available in your area. The new Armalite rifles are decent but not considered tier 1. Stag is good, especially if bought like ours here at Colt specs. Lots of choices out there.