Another point to consider when debating the AR10 vs AR15:
The AR15 is based primarily around the M4 . Most of the manufacturers of AR15s ensure that it is close to the M4 in order to pick up possible military/LE contracts. Because everyone (with a few exceptions) isn't straying too far from this, parts commonality is widespread. Should you wish to upgrade or change parts out, you will not have to worry too much about if it will work on your rifle.
The AR10, however, is far more proprietary when it comes to parts. Armalite, DPMS and Knights Armament all have their own specifications and other manufacturers usually spec their parts out based on those three. Parts such as barrel nuts, handguards, what brand of magazine you use and others may work on one but not on another. It is not a big deal, but just something to consider.
Good equipment will never be a substitute for good training.