I've owned a 3" 65 and a 2" 64, and have shot them back-to-back. I'm far from being an expert marksman, but here are my observations/opinions.

As far as accuracy potential, I didn't see a difference, though someone more skilled than me might be able to tell a difference at longer distances. The 3" did give me slightly faster follow-up shots than the 2". However, the 2" was noticeably quicker out of the holster for me.

The 3" does have a longer extractor rod so extraction can be more positive, but there are two points to consider. One, in real-world self defense shootings, reloads are very rare, and when they do happen they tend to not have an impact on the outcome. Two, the reloading technique I use involves pointing the gun muzzle up and then smacking the extractor rod with my palm. While I've never had a failure-to-extract with this technique using either 2" or 3" guns, there may be a higher likelihood of bending or damaging the 3" gun's extractor rod with an imperfect hit because it has more leverage than the 2" gun's shorter extractor rod. A damaged extractor rod can render the gun inoperable, whether it happens during an actual confrontation or during practice.

I carry IWB, and for me the 2" gun is a little bit more comfortable than the 3" gun, particularly when sitting. But this can depend on one's body size and shape. Some people may not be able to tell a difference, and carrying OWB may be even less of a concern.

Last point...How difficult would it be to replace a 3" K-frame versus a 2" K-frame if something were to happen, i.e. confiscated as evidence in a self-defense shooting or, more likely, some kind of mechanical breakage or even theft?

For these reasons, as much as I like 3" K-frames, for defensive/carry purposes, I'd probably lean towards a 2" K-frame, especially if I'm sticking with .38 Special ammo.

Just some things to consider.