I would not spend more than $400 cash for a 4" Security Six, and even that is a tad high in my opinion, but it would have to be very nice. I don't think the trigger job adds much to the value. I bought a perfect Service Six in 4" (no box, though) for $345 on gunbroker. With shipping and FFL it came to about $400. A 2.5" Six would bring about $50 to $75 more than a 4".
One thing I really like about the Rugers is how you can completely disassemble them with only a dime if you don't have a screwdriver. if you do buy the 4" Ruger, you can change the factory skinny grips to factory wood targets. CDNN has factory wood Ruger grips for $10.
As for rubber on the 65, I had the Pachmayr boot grips and it felt great. For conceal carry, the wood is better because it doesn't grip to clothes
If you're going to conceal carry, the Ruger shouldn't even be an option. That 1" does make a difference, not to mention the square butt on the 4". The 65 is the way to go as long as you understand that you're not going to be shooting alot of .357, and even then, make it 158 grain. And clean that forcing cone well. For open carry, home defense, or range use, I'd go for the 4" Ruger.