As far as skill maintenance goes... run a few sets of double-taps from the holster, 3-4 round engagements from low ready and finish with some deliberate shooting at 50-75 feet. You can do this on about 30 rounds a week.
I am fortunate in that I can walk 200 yards to shoot, shoot anything I want any way I want, etc. If I had to drive & pay range fees fees, I would certainly shoot less often, perhaps once-twice a month, and I'd burn more ammo in a single session.
I carry both subject calibers, on and off duty. While I will always choose the larger bore, I doubt there's a substantial difference in their effectiveness.