Unless you hand load, I'd steer towards the .357 GP100 just for simplicity and cost.
When I had my .454 Super Redhawk (7-8 yrs ago) I had a hard time finding decent loads in 45 or 454 and when I did they were about a buck/rd.... not for plinking.
Same with my .44 SBH and (at least at the time), .44Spl cost more than magnums.
My old .41mag Redhawk suffered much the same fate... safe queen, then sold.
Either gun will serve, but you gotta figure in the cost of feeding it. Depending on how much you shoot, that is a factor.
BTW... I regret selling all three of those guns but with a family and bills I had to do what I had to do. I might make a different decision now.
Speaking of regrets (last thing, I promise), in the 90s I kept my 4" GP100 and sold a similar Colt King Cobra. A dumb move on my part, but who knew the Colt snake guns were going to appreciate like they did. I was satisfied w that decision until I saw what the Colts were fetching at auctions years later. Oops.