.40 and .45 are two totally different animals. .40 cartridges are pushing 35,000 psi, while .45 is only 21,000, so the recoil on .40 is going to be a lot snappier and unpleasant. Make it a compact weapon and it gets even more fun. Most .45 loads are so slow they're subsonic, so it's a strong recoil, but not quite as brisk.
I'm bringing a lot of personal bias in here, but IMO if you need something bigger than 9mm, a 1 mm increase in diameter seems like a poor compromise. Personally, I'd try and find a .45 that fits my needs. I realize there are a lot more .40s that do that in the compact segment, but there are still plenty of .45s.
But please, do not take my word for it, or anyone else's here or anywhere else for that matter. Try out a compact version of both and decide for yourself.
Some options to look at:
Walther PPS .40 (single stack mag)
Springfield XD compact .45 or .40
XD subcompact .40
Beretta Px4 Storm compact .40 (in .45 if you can carry the full size version)
SIG P229 .40 (if your budget isn't too constrained)
SIG P239 .40 (single stack mag)
And then don't discount the concealability of a short slide 1911. The single stack mag makes them very slim. They're steel so they'll be heavier, but that'll help with recoil.
I'm sure others will chime in with more that I'm forgetting.