Capacity is probably the very bottom of my priority list. I'm from the old school. If I can hit and accomplish my objective with 7 shots; then I have absolutely no business with a gun in my hand.
As for the question of BEST caliber, firepower, accuracy, penetration, etc... I don't believe that there is an "All In One" gun that meets the criteria as to being the BEST in all of those categories. I don't believe that the gun exists. Shot placement, IMHO, is everything. Concealed carry and Home Defense are definitely 2 different things. Concealed is for self defense and will almost guaranteed be within 10 yards. (30 feet). Home defense can be many different scenarios. But for concealed carry, where you are generally in public, where the BG is about as nervous as you are because a street scenario is pretty much impromptu. You pulling a gun out on the BG, Doesn't matter WHAT IT IS, is a scenario that he didn't even consider. If he considered you having a gun, he NEVER would have chosen you as his target. The overwhelming majority of people DON'T carry a gun, and the BG is playing those odds. Pull out anything and you have, I would SAFELY BET a paycheck, a better than 85% chance that the BG is going to turn and run. Which bring be back to "Shot Placement". I feel probably 95%+ just as confident carrying a 32 auto as I do my 45acp. And the only reason for the 5% difference has nothing to do with the caliber. It has to do with the 45acp being a SigSauer P220. Other than a revolver, I probably couldn't find a more reliable and accurate gun. If the 32acp guns I have were a SigSauer also, I'd put my confidence at 99% of the 45acp. And the only reason for the 1% difference is because the 45acp is a bigger bullet, therefor I have a greater chance of hitting the vital organs/tissue I am aiming at.
So; I put all my faith totally in shot placement. That only comes with practice. Both physical and mental. I don't care if I have a 32, 380, 9mm, 38+p/357mag, 40sw, 44sp/mag, or 45acp. I feel equally confident in my ability to shoot where I aim and want. So, as long as the gun is accurate and reliable, I am happy. You can take the firepower, penetration, caliber, etc.... out of the equation. If you can hit what you aim at, and know what/how to aim for success; the rest doesn't matter at all.