The price may be close to the same, but the "features" are much different... they may look alike, but that is where it ends.
I don't mean to be rude, but you keep saying "compared to the Colt", but it doesn't seem to me that you understand what the Colt is or has to be compared to.
The Colt LE6920 is the closest you can get to the rifle that our troops carry. It is "mil-spec" in the sense that most of the parts come from the same bins and have most of the same testing as those meant for military rifles. It comes with a full auto BCG (even though it only operates as semi auto), 4150 CMV barrel that is chrome lined, heavy buffer...
If you want the same type of gun that the military carries, then go with the Colt.
The S&W line isn't built quite as robust. Most of their rifles use salt nitriding vs. chrome lined barrels. Many, but not all, of the barrels are 4140 steel, not 4150. All the bolt carriers are the lighter, semi auto carrier type. The buffers are lighter as well. Many of these things may be cheaper for S&W, but also many of these things really don't make a difference to the average shooter... but it is good to know that the differences exist and what they are.
Basically, with the Colt, you are getting a very solid, basic no frills carbine that is the baseline that all others are judged by. For the same money in S&W, you get more tangible features, such as free float quadrails on the 15T, or Magpul furniture on the MOE.
Hope that helps.