I picked the .45.
I've fired the G20 and it didn't feel comfortable in my hands. Plus potential for overpenetration with full-hunting/sd loads.
I have held a Beretta M9/M92, and it also felt too thick for smooth transition of DA to SA shooting without changing grip.
I like revolvers and almost went with the .357 option, but would have been shooting it with .38+p for home defense, so I don't have over-penetration through a wall and hit my daughter [.357mag loads]. Probably over-thinking it, but may not be. Also, cost factors for an 8-shot .357mag.
The FNP in .45 is the one that fits my hand the best, which means I am more likely to hit what I am aiming at under stress. I am comfortable with .45acp rounds as well.
I had a problem because you are asking us to choose between both platforms AND calibers.
I'd rather have a caliber question OR a platform question, because my responses would be different based on the change to either.
For example, if the survey was:
Glock G21 .45acp
CZ7b 9mm
S&W M&P .40
Ruger GP100 .357mag
I'd pick the M&P .40, even though it is the round I like the least of all 4 on the list. However, it is the platform I can control the best [of the semi-autos] and has the round count advantage over the GP100 [which I wouldn't use full-house magnum loads in for house defense for reasons given above].
And, if you used either set of options with the question of while hiking or outdoors, I'd go with the .357mag revolvers.
Those are my reasons.