As I think about it, it seems like a K-frame would be faster to reload. Less metal between the chambers means there's less stuff for you to misalign your speedloader on. Lighter weight would let you drive it faster, and with 125 PF loads the lessened weight would be a problem. Less cylinder mass to get moving seems like it would impact trigger pull. (And cylinder stop / cylinder life).
So, really, are the apparent advantages worth it? Or would the time I took to compose this very post been better spent shrugging the idea off and just dry firing?
Adjustable sight, 4" K-frames aren't terribly easy to come across around here, though the local shop has a new 4" 67 (complete with visible layer of dust) for $398. Plenty of model 10s and 64s for a bit less. I also don't have any K-frame sized Comp IIIs, and I'm not sure if my carriers or holster can be tightened down enough to work with a K-frame. So, the total cost is probably going to be in the neighborhood of $500 to convert to a K from an L. Worth it?