The recent White Oak Armament upper I bought I opted for no threaded muzzle for a flash supressor. As Mr. Roberts stated, a plain muzzle with no flash supressor will be marginally accurate, so it's not much of an issue. But understand that an improperly installed flash supressor will cause degradation in accuracy. For a regular rifle, go for the flash supressor. If you are shooting matches, I think you are better off without the flash supressor. The only real benefit in a target shooting application is that the flash supressor serves as a great muzzle/crown protector.
After the Clinton Assault Weapon Ban forced high power shooters to go with plain muzzles, that's when they noticed that accuracy actually improved overall. That's why you'll see rifles even now, without flash supressors.