I'll second or third any vote to pick up the S&W Mid MOE version as I got a NIB M&P15 MOE Mid MAGPUL® Spec Series in 2013 after my son 'appropriated' my custom RRA mid CAR some years before. While I still had my full size RRA A4 set up with scope for long range shooting, I missed a light carbine so I went looking for a replacement.
I liked the S&W right off because I'd modified my RRA over the years into a light weight, 14.7" bbl with welded on FH, CTR buttstock, and MOE HG with flip-up rear sight so that it ended up looking very much like the S&W so it was a natural choice. And yes, my barrel is accurately a lightweight version. It's a great choice that's set up ready to go without any modifications. That said, I did one small mod, I removed S&W's long FH and installed a std A2 FH instead (after picture below) as I like that look better. Other than that, it's remained stock since I got it.
Out of the box it ran great and I'm very happy with it, however, I do miss the RRA's far superior 2-stage trigger. Not that it's necessary as this isn't a precision shooter, however, I do have it on my other AR an am use to it. That being said, with some 6K rds through it it's run like a clock and never missed a beat. Accurate as a light weight and so well thought out all I've added is a 4" side rail for a light. Great carbine right out of the box!!