Just to offer up some info... (( and by the way I like the way you think) A 500 special with a 440 grain Cast bullet with 26 grains of H110 should put you a little over 1100 FPS out of a 5.5" barrel.
You said a 350 grain bullet and A 350 XTP w/33grs of H110 can get you 1354FPS or thereabouts.

SO,,,, Special or JRH You would not be handicapping yourself in my opinion to go with the Special. Either is going to get the job done IMHO $$ 2 cents again.

Whit cool photo, I never have seen them side by side and it would be cool to have a 500 magnum with them in another photo.