Re: 44spl/44mag vs. 45colt/454 casull?
To answer your question, Yes the 454 Casull will produce pain!
The reason the person is selling the Ruger Redhawk in 454 is probably either it recoils too much or the ammo is too expensive.
I bought a Ruger Redhawk in 454 Casull a number of years ago, and my first experience with it and factory ammo left an impression on me. The Winchester 260 grain load produced a velocity of 1800 ft/sec over the chronograph that I was using. If you don't think that you can feel that recoil you only have to shoot it a few times. I later loaded it down with a cast bullet at 1500 ft/sec and even though it still recoils it is not too painful. I have a scope on the gun and that helps tame it a little.
What you can do is buy the 454 and shoot 45 Colt ammo in it. Most factory 45 Colt ammo is very tame, so you can shoot as much as you wish. If you want more power just use 454 Casull ammo.
Another option for you is a Ruger Blackhawk or Vaquero in 45 Colt. I have a 45 Vaquero and I load it with 255 grain bullets and is pleasant to shoot. Because it is one of the strong Rugers I can load it up close to the a 44 Mag..