I'm not familiar with the S&W M&P ARs but after my abandonment of my fiberglass stocked M1A (damaged in a fire, stock replaced with GI wood; I hated it) so I switched to ARs. I had my first built to my specifications - a Bushmaster M4 type which looked like this:
It's upside down for some unknown reason. Long since sold, too, but it makes my point.
My point is, besides the olive drab "furniture", I insisted on the removal of the carrying handle (if it had one, I can't recall) and the mil-spec front sight thing. I wasn't interested in any electronics but, instead, I wanted a perfectly aligned pop-up (or flip up - by whatever name) sight system. This made the rifle trim and slim and the sights were out of the way for storage or carrying in a case but were ready immediately for use when I needed them. A very excellent system when it's put together correctly. If the S&W Sport can handle that I recommend it.
BUT! Then I needed a replacement MSR (didn't I??!!

) so I sprung for another Bushmaster package at a good price but this one came with a red dot sighting system.
Bushmaster X15 ES2
Now I found myself on the other side of the aisle, so to speak, with basically the same rifle but without iron sights. Personally, I think it's a mistake to not have BUIS but this red dot optic is zeroed and is spot on so I don't complain about it.
So, that's just some perspective for you, both sides of the discussion, I guess.