Conventional 1.5 x 5 scope for about 5 years, usually kept on lower end of pattern. Turkey hunting is basically like rifle hunting, need to put a heavy load of shot in the head/neck and a scope helps make sure you keep your head down and the shot where it needs to be. And if you have a wary old Tom that won't come in all the way, the scope provides the accuracy for an instant kill out to 40 yards. Sights can do the same, but as you age it gets a little harder to keep all of the different planes in focus. :>( At least should have sights, not just rely upon a rib.
A friend has a red-dot that he got for slug hunting, intends to use it this spring for turkey as well.
Either would be a disadvantage on a moving bird, but shouldn't be doing that with a turkey anyway, too much risk of a crippling shot that doesn't lead to recovery. Scope helps make the first shot count.