I have had both in many sizes. I find the S&W more balanced and the trigger is way better than anything Ruger makes. My Super Redhawk was built like a boat anchor but had issues with light strikes on primers. After talking to a well know gunsmith, he explaned it is a short comming with the Rugger and transfer bar. In the end the Ruger was to unrefined and heavy for what advantages it brought.
I also found the 8 3/8" barrel unfluted on the M29 is nice and by far the easiest long barrel to carry, but my chronograph results didn't give as much speed as I thought it would do compared to a 6" barrel. I was shocked and found the 6" unfluted barrel to be the best overall performing hunting and carrying 44magnum. I have had 3 S&W 29/629 models and 1 Ruger Super Redhawk 7". I came back to the S&W 629-6 6". It is a tack driver with everything I load up and carries like a dream. I also don't find any quality difference between the newer 626 and my old 1981 M29. Fit and finish is outstanding on the new Smith and Wessons 629's.