We live in a time when the number and variety of perfectly serviceable "fighting" pistols is considerable. This truly is the "Golden Age" of firearms.
I don't care if what's in my hand is a Glock, an M&P, an HK, a SIG, a Walther, a CZ, an XD, or a 1911. Any of them, properly maintained, is likely to serve well. But the first seven of them generally offer greater capacity and (right out of the box), possibly better reliability.
What I think is important in a "fighting" pistol is reliability, shoot-ability, capacity, and potency. For that, my preference would be for the larger size models, chambered in calibers .40S&W or .45. You can have that, pretty much, from any of the brands/designs I listed above.
So, I'd say select whichever of those seems to suit your fancy the best, do your part well, and you're likely to make out ok!
Personally, if I had to walk out the door armed with only one pistol, to face a fight... I would take the M&P40 (16 rounds of 180 gr. HST) or the SIG P320 40 Full Size (15 rounds of 180 gr. HST). The combination of caliber potency, easy rapid-fire control-ability, and high-capacity offered by those models totally works for me. I am also very much a fan of the G21SF, G30, M&P45, M&P45C... but capacity in .45auto caliber typically falls a bit short as compared to the .40S&W models - and I feel that "fighting" may easily consume capacity quite readily.