There are some very accurate high velocity rounds out there, CCI Velocitor is pretty accurate. The reason people usually say the low velocity stuff is better has to do with bullet uniformity being poor.

the real question is what does Matt intend to do with the rifle. A 4 MOA rifle from field positions with open sights is great for me, or does he want a slow fire tack driver with 4 grand in glass on top of it being shot off of sandbags?