harrismasher,

i have owned both the 640 pro as well as a 686-4 "plus" with 2.5 inch barrel.

both great guns.

from what you said in your opening post, it doesn't sound like you have a practical need (carry, HD, or range) for one over the other.

so, I suggest you listen to that little voice inside that will tell you which one will float your boat and make you smile the most. If they were both laying side by side on a table, which one would you grab first?

good luck with your decision. hope we get to see it like the other great photos you've shared.