The Ruger SR-556 compares to the S&W M&P15T.
The MSRP of the SR-556 is $1999.
The MSRP of the S&W M&P15T is $1888.
That's a difference of $111.
Both have M4 style six position telescoping stocks, Troy battle sights, Troy quad rail with covers, and a flash hider.
But the Ruger comes with a Hogue grip and three Magpul 30 round magazines where the S&W comes with only a 10 round magazine (I'm not sure how many though).
The Ruger is also a four position gas piston recoil system. The price advantage of the Ruger (as apples to apples as can be done by using MSRP instead of various actual selling prices) is obvious. The gas piston can be dialed down to 0 so that brass is not ejected and the rifle can be used as a single shot. For target handloads, the system can be set on 1. For standard loads, it can be set on 2. If the gun is fired 1500+ rounds in the desert without cleaning because your life depends on it and you haven't had a chance to clean it and it starts to hiccup, you can set the gas piston system on 3 and keep firing away. The piston system also keeps the bolt remarkably clean and reduces felt recoil.
Reputable dealers are selling the Ruger SR-556 to past customers for $1450. I think that's a steal for what you get with the rifle.
Of course, this is the only way the Ruger comes, so if you don't like it as is, you're out of luck. Cudos to S&W for having so many AR variants in their lineup. But I liked the Ruger alot.
As it came from the factory 2 weeks ago:
30 rounds, offhand, standing, at 25 yards using the iron battle sights:
1 1/2" three shot group with a Leupold 3-9x44mm VX1 temporarily mounted:
CAA/Ruger folding verticle grip, Streamlight TLR-1 LED light, BSA red dot reflex sight, and a dual sling ring mount with Tactical Tailor single point CQB sling:
-Steve