Ha ha, I went through the same thing not long ago.
I went with the M&P 40c for just about the same reasons. I've had it for a little less than a year and I never did get either conversion barrel.
The cost of the barrels was kind of prohibitive, as well as the high cost of magazines (for 9mm), and .357 sig ammo. But at the time the peace of mind of my options open is what was valuable to me. Not HAVING to choose/limit myself. I'm still curious about what purchasing a different gun with my money would have been like but I'm not disappointed. My M&P 40c is the most accurate gun for me that I own besides a 6 inch Model 27-2 revolver.
Minor point - If you plan on doing IDPA, from what I understand they will not let you compete with a conversion barrel in.
I was more used to 9mm but now I've bought and shot a good bit of .40 in my new gun as I was exploring the new caliber and the new pistol. The recoil IS different than a 9mm. Have you shot the M&P 40? If you can find a range that will let you shoot it side by side with the 9mm that would be great. Recoil is not snappy or painful but my muzzle ends up pointing a bit higher than it would in a 9mm. It's not bad at all.
A related story that might help: a good friend of mine went a similar route in the Glock world: a Glock 23 in .40 with a Storm Lake conversion barrel to 9mm. He would practice in 9mm and was really proud of the savings. He went to a Front Site training course and shot cheap steel case Wolf Ammo - no problems and really cheap in 9mm. The course required A LOT of rounds and had no problem with him using conversion barrels so that was a good move. He shot better with the conversion barrel - no barrel related malfunctions (had to switch magazines though), and instructor was impressed with the accuracy of his barrel (so he says anyways
) However, when he got back and resumed his own training his shooting was a bit different with the .40 barrel in place. He's decided to now practice in .40 especially since he'd been carrying in .40 the whole time. Being trained in 9mm was helpful in learning skills before the trigger pull (and there is a lot to learn - drawing, moving, stance, grip...) and a bit less helpful in learning his own gun after the trigger pull.
.40 is more expensive generally, by a few bucks per box. BUT there is a way around that. Reloading. I'm going to start in a month or so. And you could reload in 9mm too if you go that route.
I don't regret getting the .40 since I really wanted to do something new and explore the new caliber.
My follow-up shots take a little more time because of the recoil and compact size (of course I could always shoot fast and sloppy) and that will improve with experience. If i remember correctly the .40 and the 9mm versions are the same weight and same dimensions.
Good luck to you. It sometimes helps me to remember to keep things in perspective. When I get into a researching frenzy i forget that this gun is not going to be the main focus of my day unlike it is now during the research period - making it seem much more important than it is. But it also helps to remember that I'll probably get another gun eventually so no pressure
This is probably not my last gun so it doesn't have to be "perfect".
