The FBI has a specific set of criteria that they released, both in terms of how a round will be tested (there is a standard for both pistol and rifle rounds), and what the results need to be. Hornady has it up on the website IRCC if anyone wants to read through it. The FBI also does extensive controlled testing to see how various rounds perform. The data they gather is proprietary, and is not for public disclosure (get with the FBI if you have heartburn with this, I play by their rules) and is only available to LE agencies.
With that said, no major manufacture is going to release a round in this day and age that doesn't meet the FBI's testing requirements. No LE agency will buy it, and that's where the money in defensive ammo sales is, in large LE and Federal agencies. How each round performs is different from round to round of course, but here are some general guide lines.
Top Tier defensive ammo from the major manufactures (ATK, Hornady, Winchester, Remington) are all going to perform extremely well and you're probably going to need a micrometer and good steel machinist ruler to tell a difference on the tests. Bonded ammo does better on barriers, but gives up a little bit of performance in expansion. Non-bonded rounds tend to expand a little better, and a little worse on barriers. A round that expands more tends to penetrate less, and vice versa.
-Jenrick