Testing in such mediums (gelatin, water) yields measurable, recordable, repeatable data (not anecdotal heresay) such as average expansion, penetration depth, and amount of tissue damaged in the wound track which are indicators of performance and effectiveness.
Here is where we must agree to disagree. I agree that that is an indicator of performance-in the test medium. It is great for comparing bullets against each other, however, I just do not see a parallel on street performance. One would be better served to focus on tactics and skill than worry about the latest wiz bang bullets.
I generally use the same ammo I did 20 years ago, it worked then It will work now.