Hi, Dr. J.,
I'll vote for the 3". For most methods of carry, the extra inch won't matter a bit and the longer sight radius makes it better for moderately long range (25 yards). FWIW, I have put all 5 in a foot at 100 yards, firing double action with a 3", two hand hold. I recommend avoiding hot loads for reasons already mentioned. Practice with .38 wadcutter first, then practice with the carry load.
Jim