Being a cynical old geezer, I tend to go with the assumption that Plan A can always fail, so Plan B needs to always be in place. In the example you posit, Plan A's assumption of bullet expansion can fail, so the Plan B needs to be a bigger bullet. For that reason -- in winter, when the opponent can be expected to be wearing heavy clothing that plugs a hollow point and prevents expansion -- I'm partial to the larger caliber.
It's December, full blown winter, if not as bad as it's going to get in the next couple of months. In the last couple of weeks, I was in Richmond for a fatal shooting case: pretty chilly, but not super-cold. Carried as primary a Smith & Wesson M&P357C loaded with Speer Gold Dot 125 grain .357 SIG, a round designed to pass heavy clothing protocol tests. Carried the same gun the following week in Miami (doing a training film for Panteo Productions), where the weather was (for there) unseasonably cold, occasionally getting below freezing.
This past week, concluding today, was in New Hampshire. Weather occasionally below zero and consistently very cold throughout. Carried Ruger P345 with Federal 230-grain HST +P .45 ACP.
Next week will be spending Christmas in another frozen wasteland, expect to carry Glock loaded with .45 ACP Winchester Ranger-T 230 grain.
Just one guy's opinion, but big bullets have always made more sense to me in cold weather/heavy clothing environments.