I am interested in getting an AR-15, although I haven't spent much time with them yet. I assumed I should get a mil-spec(ish) Colt, Armalite, DPMS, etc., but I recently came across the Sig Sauer 556 Classic for sale. I was wondering what pros and cons would be involved with the Sig version, e.g. interchangability of parts, accessories, reliability, repairs, etc.? Thanks!