I would say everything else:What's the difference between a Super and Standard GP100 besides the grips, Barrel shroud and cylinder?
I am puzzled why Ruger didn't do the same and make SRH with Redhawk barrel, to get 41magnum, 44 magnum, 45 Colt, 454 and 480!?"
That makes two of us that are puzzled. If Ruger had done this they could have reduced the number of parts they would have had to maintain in inventory, reduced having different assembly processes and more. In the past I have had only Redhawks and GP100 and never a Super Redhawk (mainly because of appearance-the Alaskans weren't out then). If Ruger were to use SRH innards I would be all in for a .44 or .45 model in 4" bbl. Hamilton Bowen does offer a conversion of a SRH to use a RH barrel but it is a bit pricey for my pocketbook.
The only reason I can think why Ruger would not change is that current RH sales are doing ok.