Best bet would be to put in some leg work at a gun show or couple of gun shops and handle each of the ones you are thinking of buying.
Most of us have picked up a certain rifle and had it just "feel right" in our hands.
You also get a better idea of prices and features available that way.
Three items I consider when purchasing are:
1. Is it Mil. Spec.? If not there is no assurance that aftermarket parts and gadgets will work.
2. Is it 5.56, or .223? If it is 5.56 it will feed and shoot .223.
.223 chambered barrels will not safely fire 5.56 ammo.
3. Chrome barrels last longer and are lower maintenance than non lined, the trade off is that non lined have a SLIGHT edge on accuracy, So what will it be used for, Plinking or competition?
Good luck in picking one,The names you have listed are all good choices.
And as the battle cry goes, GET ONE OF EACH! [:D]