I too am new to AR's and had this same decision last month. I went with a Sport. I have yet to shoot it though, I want to replace the buttstock first for a Magpul. I'm in a non "Free State" so I have to pin it.
Anyway...to me, that rifle was a great value and quality materials. The lack of FA didn't bother me as much as the lack of DC. I really would prefer a DC, but this review eased my a fears a bit. http://www.thetruthaboutguns.com/201...on-mp15-sport/
Once I'm done with the buttstock I'll have my mods complete. I'm running an EOTECH XPS2-2, I replaced the foreend with a Troy quad rail as well. It looks pretty slick right now!