So you want an AR-15É
Brand:
Stick to a major name. Remember the best are A,B,C. (Armalite, Bushmaster, Colt, (not necessarily in that order). Also highly recommended is Rock River Arms.
Colts retain their resale value better than any of the others and have the best finish. Best functioning out of the box, but poor customer service if you have problems. They are usually more pricey than the others.
Bushmasters have great fit and finish as well as a smooth operation for a reasonable price. Quality and value. Excellent customer service. Good resale value.
Rock Rivers are equal in quality and value to the Bushmasters. Good reputation for quality and service, but haven't been around as long as Bushmaster. Not as good resale value as Bushmaster or Colt.
Armalites are high quality rifles, but are a little more costly and temperamental than Bushmaster and Rock River. Not as prevalent as Bushmaster or Colt. Good resale value.
Type:
Pre-ban - (Produced prior to Sept. 14, 1994) - Typical Price Range: $1,200 - 2,000+
Has a detachable magazine and at least two of these "evil features"
bayonet lug,
flash suppressor or threaded barrel
pistol grip
collapsible stock
grenade launcher
Post-ban - (Produced on or after Sept. 14, 1994) - Typical Price Range: $600 - $1,000
Has a detachable magazine and only one of the above "evil features." In the AR-15 line it is customarily the pistol grip.
NOTE: It is illegal to put two or more of the "evil features" on a post-ban rifle.
The basic function of these two types of rifles is identical. Semi-automatic.
Pre-ban rifles usually cost 50% - 75% more than post-bans.
You can still find pre-bans unfired, new-in-box (NIB), but you'll pay big bucks for them.
Bottom Line:
If you're going to buy a pre-ban, I would go with the Colt. Resale value will be higher and Colt made the highest quality product prior to '94. They've since changed a number of features, not necessarily for the better. Colt was the primary gov't supplier of M-16s and prior to '94 made the "Cadillac" of AR rifles at that time. Close second: Bushmaster.
If you're going to buy a post-ban, I would go with the Bushmaster. This is a less expensive rifle that is just as functional as a pre-ban even though you can't "trick it out." Bushmaster is now making them for the gov't too. They will give you the best bang for your buck. Close second: Rock River Arms.
Regardless of your choice, make sure the chamber is Mil-Spec, not SAAMI Spec. This will allow you to use virtually any type of .223 / 5.56X45 / NATO ammo.
Be certain that the chamber and barrel are chrome lined, unless you intend to shoot in competition and keep the rifle in immaculate condition at all times.