If ammo cost is a factor to you go with the 9mm. Capacity also goes to the 9mm. Really just depends on what you like. The difference in the wound channel produced and energy is pretty minimal with good ammo. I shoot all my 9mm handguns more than all my others just because of ammo cost.
"They're on our right, they're on our left, they're in front of us, they're behind us; they can't get away from us this time."
Chesty Puller, USMC, Chosin Reservoir, Korean War
"You cannot exaggerate about the Marines. They are convinced to the point of arrogance, that they are the most ferocious fighters on earth - and the amusing thing about it is that they are."
- Father Kevin Keaney, 1st MarDiv Chaplain, Korean War