Well, that rather depends upon several issues. A well trained, practiced, dedicated shooter at a match where he knows he is about to shoot a clearly identified target and is using both hands can, at realistic close combat ranges, shoot identical scores with any of the self defense calibers in essentially the same time. However, this is a game, not real life.

Now, let's move into the real world. The 9mm is easier to shoot accurately and at speed with less sustainment practice. This is particularly true when using only one hand because the other holds a cell phone, your kid, your wife, a car/house door, another bad guy or other things you can't readily dump on the ground. Engrave it into your mind that shot placement is the single most important component of the ability to incapacitate an assailant.

Non-dedicated personnel, and many honest dedicated personnel, find that the .38/9mm provides them with optimum ability to accurately and quickly place rounds on a target under less than optimum conditions. These can include head colds and various other conditions that lower your physical/mental ability to perform at less than your absolute best. If we look back at the first paragraph, when was the last time you went to the range/a match with a fever and stuffed up head? I haven't done either when sick, but I have attended several matches after a night shift.

I'm not sure what the relative magazine capacities of your .45 and any 9mm may be. More is better. Running out of ammo before you run out of bad guys isn't likely, but possible-and REALLY bad- during any realistic self defense situation. Not necessarily of an excess of bad guys, but because of slow law enforcement response.

If you're confident of your abilities with the weapon/caliber of your choice, good for you. Just make sure you're looking at all the factors.