The very best data you can get is on the range. What do you want the ammo for? Hunting? Defense? Target? Plinking?
All published data is a very accurate determination of how that cartridge performs in the test gun. Shoot different ammunition at different ranges at paper targets. Shoot into clay, dirt, wood. Autopsy animals shot with your load.
There is just no "bad" ammunition sold, otherwise the company wouldn't be long in business. Start with .38 Specials and shoot,shoot, shoot, and shoot some more. Your best will come to the surface.