This thread intrigued me. RavenU had the same input as my training buddy which was different than mine. So yesterday at the range, I brought a bunch of different rounds to shoot with my 9mm Shield, just to see if I could really tell the difference, including my carry ammo, Federal HST 124gr std. press. I brought S&B 115gr FMJ (my usual range ammo), Blazer Brass 115gr FMJ, Lawman 124gr FMJ, American Eagle 124gr FMJ, Armscor 124gr FMJ, and Perfecta 115gr FMJ. I did a bunch of draw and fire drills with a shot timer, timing beep to first fire and split times between shots (I do at least 3 per draw). Target was at around 20 feet (5 - six inch circles). Draw to first fire was pretty consistent with all ammo types as you would expect (1.7 to 1.9 seconds). Had a couple slightly faster and a few slightly slower. Yeah, I know that isn't very fast, but I'm working on it. Split times between shots were also pretty consistent, which surprised me. Accuracy was acceptable, all shots but one within the 6 inch circle I was aiming at (had one flyer - yup, low left - flinch). Bottom line, I guess, practice ammo, at least the ones I brought, doesn't really seem to make a whole lot of difference. Maybe if I was shooting for the fastest split times? Recoil mitigation effort and sight recovery timing was about the same for all the follow-up shots.
Anyway, my training buddy said, "See? I told you it doesn't matter". I think what does matter, is that we keep practicing and strive to improve. I now think that as long as your practice ammo is reliable and is loaded so that they are "reasonably" similar in feel, you should be ok. I don't carry +P+ ammo, and would be interested to hear from those that do as to whether practicing with standard pressure rounds throws you off. Certainly with what I use, it doesn't seem to make a difference.
ETA: Don't ask me about how much time it takes me to change magazines. holy crap! I have to practice that a hell of a lot more!