I've got the security six and a an older smith 686, both with adjustable sights and 6" barrels. The ruger got an action job, the smith got a wolff spring kit. The smith has a WAY better trigger on it and the bigger grips and full underlug handle recoil more effectively.
The ruger feels much smaller, even with an aftermarket rubber grip. felt recoil is greater, especially with the skinny wood factory grips. it's not an issue with 38's, but with 357's it can become unpleasant. It cost me half what I paid for the smith.
If I could only keep one it would be the smith, but the ruger is a fine gun. shoots great, indestructible, and I like how petite it is. I wish I could trade my blued 6" for a stainless 4" though.