Against my better judgement I will jump into this with both feet. The OP asked which way to go, caliber or capacity. My HD gun is a Glock 22 with a Streamlight TLR-3. IMHO, the weapon you choose should be one you are the most familiar with and can shoot well. Bells and whistles are great on the range, but when the moment comes, that is not the time to remember, do I grab my .45 or my 9MM------
In the middle of a crisis is not the time to grab a handgun you need to remember which one you have and fumble with a safety that may or not be there. Keep it simple and settle one ONE. Take that one and practice until the handling is second nature.
If you mount a weapon light, like I have, shoot it with the light. It does change the balance some, but once you understand the reason for the light, it too will become second nature.
Mindset and tactics are far more important than capacity or even caliber.