A consistent, hard grip on either handgun, auto or revolver is required for accuracy.
I disagree with the word "hard". I think "firm" is a better word, and less misleading. And, even that isn't
required for accuracy. Consistency (doing it the same way each and every time) is.
And, I would point out, in this case, I'm talking about accuracy alone, not accuracy+speed, which is a different matter.
The OP isn't asking about what is the needed (or best) grip for 7 yard speed shooting. He's asking about the difference(s) in grips between "big revolvers and big semi-autos.
The firm grip needed to control recoil so as to keep the pistol as on target as possible, allowing for the fastest practical repeat shots is not the only grip that can produce accuracy.
It may be the grip you use, it may be the grip
you need, it may be the grip your semi needs to reliably function, but its not the only grip that can be used to accurately shoot a handgun.
A revolver doesn't care one bit about how "hard" you grip it. And having a "death grip" on a SA revolver is actually counterproductive to using the gun the way it was designed. Now, before we get into any discussions about how "not everyone shoots a SA revolver", etc., the OP has a Super Blackhawk, so SA revolver shooting is on topic in this thread, along with discussion of grip style when shooting other designs.
People talk about putting your grip as high up on the gun as possible, and for many semis and all the DA revolvers I can think of (save one) this is generally a good idea. For SA revolvers, its the opposite of a good idea.