I have a 7.5" SRH in 454 Casull.
I have checked into the ballistics quite extensively and the 475 and 500 Linebaugh don't really do that much more if any over it.
I now load 360gr WLNGC's @ 1520fps and 390gr WLNGC's @ 1420fps and these are not top loads. If I worked on it just a little bit more I would be getting another 30 to 50fps without any problems.
Jae-Bok Young now even supplies a 420gr WFNGC .452 cast bullet which should be able to do 1300fps so saying that there are far heavier bullets available for the larger caliber guns isn't really a true statement.
Felt recoil of my 390gr loads is actually less than the 360gr loads, and the 454 bullets penetrate deeper than the larger calibers as well.
If you where to go to a 500 S&W then you would definately get a more powerful round but I feel that the handgun is just to big for carrying so takes it out of the realm of this discussion.