What do you plan on doing with this gun is the real question imo?

Carry? Don't MP it then. There can be issues with retention drills (or retention) in firing close to the body where you get blast effect in your own chin. Same for firing inside of a vehicle and seeing afterward a nice lil burn/blast mark on your ceiling liner (have seen this personally). And in any event, you ARE going to have more blast out of that 2.5" than either a 4" or 6". Do you want to divert some upward?

Range work? Your call but I think the previous posters comments (and there were a lot of them you'll note) about reducing potential resale value have solid merit. I recently passed on a 629-1 3" just because it had been MP'd and I didn't feel I would ever get the money back out of it. If you think of the persons who have commented negatively so far vs those in the positive, I think you have a good idea how "the market"will break down should you decide to sell. And the 686 2.5" is a desirable revolver.

Just my .02.