How much do you think you might shoot it? I would agree with Skeet about the ergonomics of the Model 29, they are balanced nicely and have a bit nicer trigger than a Redhawk, especially the older models with the forged, case hardened trigger and hammer (that's what I'd be looking for).
If you're going to really shoot it a lot I would lean towards the Ruger. It's a heavier framed gun that has an excellent locking mechanism on the cylinder which virtually eliminates the end shake and eventual slop that the S&W's are notorious for developing after a whole bunch of heavy loads go through them.
If you're going for a 4" bbl check out the S&W Mountain Guns, I have a 629 and a 625 in that model and they are awesome! My 5.5" Redhawk is a great gun too.
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