I have a bobbed hammer on my S&W13, as noted earlier. In response to questions about resale, etc, and as egor20 alluded in his post - if you are worried about resale value, don't bob the existing hammer. Buy a bobbed hammer, and replace the original, while keeping the original hammer in your revolver's box or in your parts drawer.
That's what I did with my 13. Original hammer is with the original stocks, in the original box.