is the felt recoil of either the .45 and/or the .40 cal. less than my .357 snub nose revolver?
Both, yes, definitely.
If you can tolerate a 357 Snubbie a Glock 27 or other small(er) 40s&w should be no problem.
I hear the XDs.45 is a soft shooter for its size.
The Glock 36 is another good one... its about the same size as the G19/23.
A scant few of the small 380's are soft shooting. The LCP is tolerable, but it jumps around in your hand and its no easier on your hide than a PM9.
Initially...I'd nudge you towards looking at and shooting the Kahr PM9/CM9 or the CW9 before moving on.
Fantastic pistols that shoot extremely well with minimal recoil for being so small and light...plus they all have a sweet trigger.