Are you saying that:
"You would be just as effective (spotting, tracking, aiming,) through a parascope vs a firing station with unobstructed views "
"Its not worth addressing (due to the subjective nature of relative turret effectiveness or other reasons)"
Because I agree with statement number 2, but it still seems like you are arguing statement number 1. Which is ridiculous.
Sure the crews had radios - but - have you ever been with somebody who points out, shall we say, a deer in the woods? Only you don't see it. Your friend describes where it is, points at it, you have an unobstructed view and the exact same viewshed. But it still takes you an embarrassing amount of time to spot it? Imagine doing that through a parascope (which, incidentally, disoriented people to the point of sickness), with the stress of battle, with only auditory help. No way in hell would it be just as easy to spot, track, and aim. Not a chance.
I have an idea. We will put you in a blindfold, give you a gun and a headset. Then a crew will call out apples for you to shoot off of imaginary heads. Don't worry, the apples can't move or shoot back.