Like usual what is the intended use?
If all you want is super accuracy get a bolt action as it'll be more accurate and cheaper for an accurate gun. Your going to be using expensive or reloaded ammo if you want super accuracy so you probably won't be throwing lead down range as quickly as possible.
If you want to do a bit of plinking or fast reaction shooting semi may be the ticket for you.
But id suggest that is what you have an AR15 for so I reckon a bolt will be your best bet.