Why not both? IIRC, the .40 Glocks can accept an aftermarket 9mm barrel as a drop in replacement. Then you can use 9mm magazines (heck, I hear that the .40 mags work in a pinch) and rock-and-roll. That way you have the power of the .40 until you expend all of your ammo, then you can switch to the 9mm if you are scrounging around the blue helmeted guys <img src="/images/graemlins/smile.gif" alt="" />

With training you can become proficient with any caliber. Premium self defense ammo is virtually indistinguishable in performance (i.e. it is shot placement that counts, not bullet performance).

I use the Milt Sparks Versa Max II for my commander 1911. Excellent holster. Pricey, but worth it. Just make sure it is mated to an equally well-performing belt.

Edit: my statement about self defense ammo applies to 9mm and above. I would be leary about using .32s or .25s as anyhting but a BUG (back up gun).

Also, if Milt Sparks is backlogged, try lightningarms.com. A little more pricey, but they have a lot on stock for rapid shipment.