I have to choose between three different .300 Blackout uppers but I want to choose the best upper that I possibly can. Here are my three finalists, and I am just wondering if any of you guys have had experience with Sota Arms, Mas Defense, or Alpha Shooting Sports?

Here are the links to the three great priced uppers.
http://www.shop.ar15hardware.com/16-...-300BOCMA4.htm
http://www.shop.masdefense.com/16-30...ES-163ORBU.htm
http://sotaarms.com/component/jshopp...2/117?Itemid=0

Thanks for any insight!