300gn: I think the load you should be looking for, regardless of manufacturer, is a 124/5 gn hp at around 1150 - 1200'/sec. This is either a +P load or a +P+ load. The standard load for a 124/5 gn 9mm is around 1100'/sec. The +P gets you to about 1150'/sec and the +P+ gets you up around 1200'/sec or a bit better. It really does not matter. All you really need from a 9mm with a 124/5 gn slug is the +P level. I recommed the 124/5 gn slug for deeper penetration, especially from a short barrelled pistol.
If you carry a sidearm for personal protection, not for a job, then the idea of a one-shot-stop won't matter - you will continue to shoot until your assailant is down and out of action, so get the ammo that functions best in your carry piece and practice with it. You can also practice with NATO loadings which, if the 124/5 gn fmj, are at about the +P level, and then carry your hps.
As the guys have said, there is a lot of ammo out there that improve the hit capability of the 9mm; before there were hps and soft nosed slugs, the routine was usually 2 shots to the chest and I do not recall ever seeing anyone get up after collecting a couple of 9s like that, so whether the assailant is immediately incapacitated or in the process it won't matter unless you feel he/she is still able to shoot you or get to you, in which case you simply add a few more rounds to the target area - as I said previously, you will most likely continue to shoot until he/she is down.
You really do not need the fastest and bad-est, you simply need what works and what will function best in your piece. jmtcw.