As touched on above, one of the critical areas is finding a defensive round that you can "emulate" in a training round.
Point-of-impact will shift, naturally, but, how the firearm performs is as key to muscle memory and training. So, carrying 147s but training with 115s leaves a question mark or two in my mind.
Now, shift in POI is one of those things that reinforces the notion that you have to be able to train with your carry ammo. So, those $6 each superdeathmagums will bankrupt you before you can get to solid confidence.
Which is why I've always been willing to use the 2nd or 3rd "best" ammo out of the surveys--when it's just enough cheaper to be able, say to buy 3 boxes for the price of two of the "best testing" ammo out there. That extra box you train with, especially if that training gets you either smaller group sizes or more confidence in impact location, is better than that "better" ammo.
So, for my 2¢ the ammo you can afford to be confident with, and consistent with, to where it's near second nature, is better than a specific brand. Not that there's anything wrong with starting from some well-tested rounds like the HST or Defend.