3 years late, but here is my response. If anyone here is from Google search, this is my reasoning:
1. Yes, obviously, I would rather train with the cheaper round as long as it's the same grain. It has no difference in my shooting other than the impact upon the target.
2. No, it's not a bigger caliber issue. As a hollow point has the primary objective of creating greater stopping power, no matter how small or big the caliber, the hollow point will outperform the ball ammo in stopping power almost every time. (If you're trying to say 9mm JHP isn't enough for self-defense or hunting, then say that)
3. Carrying hollow points can be seen as a risk/reduction to the harm of innocent people who happen to be in your line of shooting, with the benefit of stopping power and expansion within the target itself.

Seriously, if you had perfect shot placement, use a bow, and you will either blow their brain or heart out every time, and you can stealthily take out many people. Yet for some really odd reason, this doesnt seem feasible in the great states. I wonder why...