Felt recoil is perceived differently by lots of folks. Kind of hard to quantify.
I've often thought that some shooters considered it to be how hard the grip's backstrap pushes against the web & palm of their hand ... while others may focus more on how fast/hard the slide cycles ... and yet others may pay more attention to how much muzzle rise/whip they experience. I suspect that muzzle blast can distract a number of folks from all of these things, too.
I own both the G27 and the M&P 40c.
I found that using the 40c's different grip inserts has, more often than not, changed how I experienced the various factors that influence how I perceived felt recoil.
My G27 and M&P 40c both have some noticeable muzzle rise/whip. That's the nature of the cartridge, to some extent.
Both seem to get back on target quickly & easily enough, but the ergonomics of the 40c seem to make it a "more natural" effort. I don't have to work quite as hard with my 40c to get that slight forward torque of the wrist required to align the Glocks with their unique grip angle.
The amount of recoil experienced by
my hand and wrist (straight back against my hand, and resisting the torque effect with my wrist lock) is less tiring on
me with the 40c than with the G27.
I feel less wear & tear on my trigger finger when using the 40c.
Perhaps the most telling thing,
for me, is that I've noticed I can shoot more rounds through my 40c, with less wear & tear on
me, than I can with my G27 (using the same ammunition). That's only really an issue for me when it comes to how long of a shooting session I'm planning for any given range day, though. It's not a factor with either little .40 if I'm only going to be shooting 50 rounds through either of them.
I carry both from time to time (carrying my 5-shot J-frames or one of my small 9's more often than either).
I take both the 40c & the G27 through range sessions and quals fairly often. Shooting both of them is harder than shooting the similar models chambered in 9mm. (I own a couple of G26's, and while I don't own a 9c, I've spent some range time with a few of them owned by other folks.)
I find that continuing to put a lot of emphasis on my .40's makes shooting the 9's even easier.
Luck to you in your decision. I own (5) 9's & (6) .40's, so it's not like I've ever really chosen one over the other. I've also carried examples of each caliber as issued weapons over the course of my career.
I'd suggest trying to find a 40c to try out at a range somewhere before making your decision, though.