Friday night, I loaded some 9mm to try a new powder (Shooters World Auto Pistol, which I LOVE). I loaded 10 rounds each of 5 charge weights using standard and magnum powders.
On the lower charges, the magnum primer was actually about 25fps slower but had a much smaller ES and SD. Normally, I would think that the magnum primer would be a little faster than a standard primer, although I have read that there is no difference between the two. After I got closer to my top charge, there was very little difference in velocity between the two, but the magnum primer maintained the smaller ES and SD.
I was expecting a little more velocity out of the magnum primer and never thought about more consistent velocities. I learned something after loading for many years! Try that powder if you're looking for something new. I've never had a powder that metered so consistent or easy.