I won't disagree with those touting the 10mm, but in really what's it going to do that the .40 won't? Why pack around a big 10mm when you can carry a smaller .40 and accomplish the same thing? People act like the .40's going to bounce off a critter, when in fact with either one you would get pretty much identical results.
Assuming hardcast bullets, I like .38-40 style (.401") RNFP for 180gr as the meplat is pretty good and from a 4" G23 can average them at over 1,225 fps using Longshot. The really nice 200gr WFNGC from Beartooth averages just over 1,150 fps from the 4" barrel with some 800x. So I'm not exactly sure why so many think down on the .40 when it's clearly no wimp, and in fact makes a lot of sense considering the size, weight, and capacity of the weapon.
As for the 3" SP101, power wise you're fine but it's the 5 shot capacity and slow reloads that get me. Interestingly, even from a 3" SP101, the velocities can still be very good. I had one, and here's what I got:
Buffalo Bore .38 Spec 158gr LSWCHP +P: 1,098 fps avg
Remington 125gr Golden Sabre (.357): 1,238 fps avg
Remington 125gr JSP: 1,451 fps avg
Speer 135gr "short barrel" Gold Dot: 1,102 fps avg
Winchester 145gr STHP: 1255 fps avg
A few of the decidedly lower power options are in 9mm range, but trust me, even from a 3" SP101, the .357 Mag can spank the 9mm. I had some Buffalo Bore .357's but guess I never chronographed them, but according to Buffalo Bores website:
(3" J-frame)
a. Item 19A/20-180gr. Hard cast LFN = 1302 fps
b. Item 19B/20-170gr. JHC (jacketed hollow cavity) = 1299 fps
c. Item 19C/20-158gr. Jacketed Hollow Point = 1398 fps
So yeah, a short .357 Mag can utterly SPANK the 9mm.