A few questions: How are you planning to use the rifle? Regular competition, heavy use, such as in NRA highpower or CMP leg matches, or just occasionally? Are you planning to do the work yourself?
In general, the consensus for the long haul, is you cannot beat the Springfield Armory receiver. Almost all of the top M14/M1A 'smiths prefer workin on SA receivers because sometime the off-brands can be out of spec dimensionally, and is not worth the time to rework (it can be done though). A couple examples would include the rear sight, and the bolt. On a SA, its almost drop in, but on other brands sometimes it requires lots of fitting. If you are doing the work yourself this may not be an issue. If you aren't shooting alot, it may not be an issue either. When I was competing, my SA M1A was rebarreled 5x, the bolt was changed 3x, and the rear sight 2x. A rifle is a machine like anything else, and stuff wears out. If you're paying for smithwork, it becomes clear you dont want to pay extra to refit standard parts, or to cut special threads on the barrel because it doesn't quite clock right. Another biggie to watch for is the machining of the rear sight base. If things are out of square, the sight spindle will wear eccentrically, and the sight will not come out of the well "straight" when you crank in elevation.
Anyway, this response is general, not aimed at Armscor. Just my experience, and what my 'smiths have told me. In competitiion, most brands I've seen can shoot (but at what cost, and for how long).