The best way to look at it, in my opinion, goes something like this:
While there are no limits on the type of ammunition or firearm, and there are no caliber restrictions; what combination would be easiest to explain to a jury? The jury at your trial after you use your firearm in self defense will, most likely, be made up of people largely ignorant to the finer points of firearms. While 10mm is a fantastic self defense round, it'd be very easy for the prosecution to say you we're carrying a small cannon and you we're just waiting for a chance to kill someone. My suggestion is to carry a very common caliber such as 9mm, .40, or .45 Cal.
For these same reasons I also suggest carrying a bare bones pistol. A sig, glock, m&p, h&k... something fairly well known that isn't highly customized. While every firearm I own has a trigger job, I don't do much other work to my carry pistols. Using match grade sights, ported barrels, etc. can have a very similar effect.
While you and I know that these things don't make the pistol more deadly, an overzealous prosecution can make the case that you have these things to make you more efficient in your killing. We, on this forum, know the truth. How confident are you that the jury will be made up of people from here?
I, personally, carry a Sig Sauer P226 chambered in 9mm. While I own a P226 Mk 25 and a P226 Scorpion, for my carry its just a basic P226. You can carry nearly anything you want, this is just my take on it.
Basic Gun Safety by Jeff Cooper:
1) All guns are always loaded
2) Never let the muzzle cover anything you aren't willing to destroy
3) Keep your finger off the trigger until your sights are on the target
4) Be sure of your target and what is beyond it