When I was planning my Maximum 50 Caliber conversion, I evaluted both cartidges.
The Ruger Maximum will handle the .500 S&W Magnum. It exhibits no more case head thrust at 50K PSI than a .475 Linebaugh at the same pressure.
Note: Bowen and Clements will not build them. I asked.
Jack Huntington built mine, and he wouldn't test fire it himself, he has a guy who likes punishing himself that does that for him.
In my opinion, the reason to go with a long/maximum should not be to move the same bullet faster, but to move a bigger bullet at the same speed.
I picked the .500 Linebaugh Maximum over the .500 S&W because of:
1) the availability of heavy bullets (over 500 grains) due to the existence of the .50 Alaskan.
2) it's still the biggest kid on the block. I had a smith cut up a relatively rare and semi collectable revolver. I'll never look at it and say, "Damn - shoulda made it bigger".
It throws a 515 grain bullet out the end of the tube running about 1388 fps.
I have carried it concealed in a high ride pancake holster under a jacket, and it can kill an elephant. That's just cool.
I'm having a .500 JRH built as my "little .500".
Notice nowhere did I try to justify this conversion with what I "needed". I'm not BS'ing myself or you guys - I just "wanted" it.