Well Timothy, I agree with both you and Rob. I started on my uncles .45 at about 15 yrs old and shot .45 almost exclusively from that point. I'm fast and accurate with it. Better than 9mm at this point for a simple reason - my body is totally tuned to .45 after many years of shooting it on a regular basis. I know where the sights are, where they will be after I fire, and when to fire again on recovery to poke multiple holes on target rapidly - combat shooting. I can point fire, aim fire, fire with both eyes open, either eye only, two hands, strong or weak, etc. I know about how much to lead moving targets with the .45. I (comparatively) suck in 9mm for the same reason - I shot 45 almost exclusively all my life. For me to start shooting 9 now is the same waste of time others would see trying to master 45. To quote Jake Roedel in Ride with the Devil, "It ain't right and it ain't wrong. It just is."
As for 9 for most people, I agree for the reasons Rob pointed out. Let's face it, most people get just enough instruction/practice to be comfortable with a firearm and be reasonably proficient. Many on this board do not fall into this category, and I'm sure your proficiency in your chosen caliber is well above average.
As an aside, seek as much professional training as you can afford and then PRACTICE what you are taught. Shooting is a degradable skill. Aim for excellence, make defensive shooting a muscle memory activity and when your body starts moving up the condition scale, you'll not regret it.