I have played with the M14/M1A platform for a long time. Love the rifle, but it is really limited. Shooting match ammo, 1.5 MOA is about all you can expect out of these rifles. If you are not FF the barrel, then about 3 MOA at best.
The conclusion that all M1A is this: the best M1A set up is to just keep her stock and shoot her with Irons.
M1A's can be accurate to 1 MOA or below, but they take a lot of work and expense to accurize to this level, and in the end, it still will not be as accurate as an AR barrel you bolted on yourself. If an all out accurate Semi-Auto Rifle is what you want, I would stick with AR10 (or any other .308 AR that uses AR style locking lugs).
AR's are ready to be scoped, M1A's you pay a premium to scope it, and even then, the scope still will not be as stable and secure as if it were on an AR.
With AR's, all you need are some FF-Handguards to free float the barrel. With M1A's, you will need to get a Sage Type Chassis, this will run you about $800.
M1A's also have horrible cheek-weld, and to get the right site height you will have to add a doohickey-thingy. The AR platform comes ready to scope with with correct cheek weld, no modifications are doohickeys needed.
There are other doohickey's you can add to the M1A to accurize it, such as a unitized gas cylinder, NM oprod spring guide, etc. However, all these little mods are questionable if they even do anything. An AR do not have these special doohickeys and is already 1 MOA out of the box.
If you bought a barrel that did not meet your expectations, swapping them out is easy with an AR. All it takes is a wrench to take off and off. With M1A, every time you want to change the barrel on a M1A, you have to find that "magic headspace". It takes a lot of work to time the barrel and lap the bolt on a M1A, and most of the time this is done by a Smith.