Howdy,
The best advice I can offer is to disregard the notion of "stopping power". There really is no such thing, like "assault weapon". What matters is shot placement, not bullet caliber or terminal ballistics (self defense shootings happen well before terminal ballistics come into play anyway).
It sounds to me like you're looking for a gun with a touch more teddy-bear-security feeling, that a bigger caliber will make the bad man go away. Now don't get me wrong, so long as you're responsible with your gun I say go ahead and get all the security-blanket comfort you want, I certainly do with magazine capacity. Let's just be careful we don't start believing things like caliber actually make a difference. Unless we're comparing extremes like a .22LR with a 44Mag, all self-defense calibers are practically the same even-though they're not technically identical. The difference between your current 38cal and a 40cal is practically non existent. In fact you'll likely notice a difference in your maintenance bill before you notice a difference in performance.
So, drop the whole notion of "stopping power". Pay attention to shot placement instead. When looking for your new concealed carry gun, get what you enjoy shooting so that you practice often and can put the shot on target when it counts. As for which specific gun, the only way to figure that out is to go handle all of them and decide for yourself.
My concealed carry is the Sig p320c. Everything is a trade-off, and for me the larger grip, larger magazine and longer barrel is worth the slight printing. I chose 9mm over 40cal for the extra round in the mag and 9mm costs a touch less than 40cal. "Stopping power" had no part to play in my decision and I strongly advise that it have no part to play in yours.
Very pisspoor advice as far as "stopping power" is concerned.
Just out of idle curiosity.............
How many people have you shot as a means of your "opinion"?
It's funny how the 9mm crowd always says their "Wonder 9" is just as good as a .40S&W or .45acp but you NEVER hear of the .40S&W or .45acp crowd trying to build up themselves into believing their caliber was just as good as a "Wonder 9".
One of my "associates" was a HUGE "Wonder 9" fan until he had to use it in a self defense shooting. Nowadays he carries a .40S&W.
Shot placement? Sure, it's very important but it cannot be depended on happening during a high stress situation like a SD shooting.
Heck, go to YouTube and look at the various cop shootings and only about 25% of their rounds hit their intended target.
In most of these "incidents" the intended target is unarmed.
These "incidents" involve men and women that carry a gun for a living and have received many hours of firearms training and how to shot during a high stress situation.
Many, many years I go I was at a local Game & Fish range shooting a Bill Wilson LE Accu-Comp .45acp bowling pin gun and an old guy said "Pretty good shooting."
Me "Thanks!"
Old guy "Yeah, I can shoot that good."
Me "Really?"
Old guy "Hell, I can shoot that good with someone shootin' back at me!"
Turns out the old guy was my future wife's uncle and he did 4 tours in 'Nam as a 18B with the 5th Special Forces Group.
Myself, I prefer a bigger more powerful cartridge to compensate for the lack of shot placement in a high stress situation.
Eventhough handgun cartridges do NOT have massive stopping power there is a HUGE difference between the stopping power of a 9mm, even +P loads, and that of 40S&W, .45acp ( especially with +P loads ) and full power 10mm Auto loads.
Just my $.02 and your mileage MAY vary.
Paul