The Super Redhawk has a beefier frame. It has an extra 2 1/2" of frame that surrounds the first 2 1/2" of barrel. It has the scope ring cut outs, except for the SRH Alaskan, which has the barrel cut off and crowned at the end of the frame extension, with no scope ring cut outs.
The SRH has a stud grip frame like the GP100, and in fact the grips can be interchanged with the GP100 grip.
The SRH has one hammer spring, and separate trigger springs, like the GP100, making IMO a much lighter smoother trigger pull. Actually to me it feels lighter then my SP101.
The Redhawk has a full frame grip. using two grip panels. No frame extension to the barrel. Has a single hammer spring that does everything, making for stiffer trigger pull.
You can't go wrong with either built like tanks Rugers. I owned a .44mag Redhawk, but didn't like the trigger pull, and the grip.
I now own a SRH Alaskan, in .44 mag. I much prefer the grip, and trigger pull. and I think there is more grip options with the SRH.
Right now I have a GP100 compact grip on it for CCW.