The Ruger 4" RH is 5.5 oz heavier than the 4" 629 (SKU #163603). It was released long after the 29/629 with additional mass a selling point. It's no-removeable-sideplate design inspires thoughts of extra strength, even if it is cast steel rather than hammer forged and heat treated, a la the 629. The 629 was designed - and the latest versions have the latest endurance package - for standard SAAMI spec .44 Magnums. Need more oomph? Get a larger/meaner caliber!
The best thing about the S&W is the trigger, of course. The worst attribute of a Redhawk is that long DA pull, due to the one spring for hammer power, trigger return, and trigger group lock. My 5.5" .45 Colt RH was slicked up by Ruger when they did some QC repairs & replacements. Certainly, the one 4" RH I tried was no better, if even as good - but certainly nothing like my original 'rancid Redhawk' trigger was upon purchase. It is highly unlikely that Ruger would change anything in the lockwork of the RH - the run is too small. My bet is it gets a few minutes of 'tweaking' - certainly more cost-effective than changing their castings/punches.
Now prices... The MSRP for the Ruger RH is $780 - the S&W is $869. Add to that $35 for the absolute-best grips for a 629 - the backstrap padding Hoque .500 Magnum monogrips. You can only get them from S&W Accessories - or on a new .460/.500 Magnum revolver. One size fits K,L,N, & X frames. They add maybe 3/16" to the trigger pull length - but a lot of recoil absorption. My 4" & 6" 629s sport them - and both have the IL - and no problems. Here are the .500Magnum gripped 629 and my original 625MG:
I am not a RH fan - I loved my .454 SRH far more - much better stock trigger, pre or post break-in (The SRH/GP100 lockwork has a separate hammer and trigger return/group latch spring). They shortened the wrong gun. I'll keep my 629's.
4" 629Stainz
PS Comparing my SS 5.5" .45 Colt RH to my 4" 625 Mountain Gun in .45 Colt, the 625MG grouped slightly better with the same loads off sandbags at 25 yd. No commparison, trigger-wise, which probably helps the standing freehand shooting, where the S&W excelled. One screw out and the cylinder of the S&W was in my hand for cleaning, too. The 625MG sported Ahrends square conversion fg cocobolo stocks, the RH had it's original Ruger wood - which my wife preferred! In fact, loaded with 250gr GDJHP's, it was her 'house gun' (She doesn't like the 625MG!). I found a second 625MG - and sold the RH. Oddly, the cylinder wall to cylinder wall thickness measured .059" for the RH - and .062" for the S&W - not what you'd expect, that's for sure. I don't miss the RH... but I really miss that .454/.45 SRH!