I'd pick the one that felt better, and not worry about the other stuff. What your hand likes and your eyes can pick up quicker will matter more than anything else. Both are great guns, as witnessed by the sales over time. The Smith has a better trigger, and can benefit more from a trigger job, the Ruger will outlive you, and probably your grandkids as well.
As to carry, I've carried four and five inch barrels without any problem, barrels aren't the problem with concealment, the grips and the grip frame make a lot more difference to me, because I'm pretty small-framed. On duty I used to carry a Smith 681, but never carried my own personally-owned 686 until I round-butted it, it made a lot of difference in the concealability. My current favorite is an M-65 Smith with a 3-inch barrel, and it goes everywhere with me. I can't shoot snubbies worth a foop, but a three-inch in my hands is as good as a four-inch, and carries a lot better. Truth be told, a small auto probably carries better than anything, but I'm a dyed-in-the-wool revolver man, and always will be. Either gun will serve you well, you have to decide which fits you best. But packing a gun is the least of your worries, first you have to become a good shot, and train properly. Getting to Carnegie Hall and being a good shot both require the same thing.....practice, practice, practice! :wink:
Papajohn