My experience: the SP101 recoil with full bore ammo is considerably more than a 4" Smith 38 with NON +P ammo. I don't have a 357 that is that small, so can't compare directly, but it is more than the recoil of my 4.5" 357 Blackhawk IMO. As mentioned, it depends on the ammo you choose. The 115 grain SD loads WILL 'get your attention'! No pain or anything like that, but "substantial". Of course in the larger guns, (GP100 and BH), it will be substantially less. I haven't tried either of them.
One thing of which you should be aware: The hammer spring on the SP101 is THE stiffest I have ever seen! My wife liked the gun, but after cocking it a couple of times (to shoot single action), she handed it back and showed me a red, sore, thumb. "No dice". I changed out the hammer spring, and the trigger return spring (courtesy of MidwayUSA), and now it is reasonable. And the trigger pull has decreased significantly as well - even in single action shooting. My shooting buddy tried mine, and immediately ordered out and installed the lighter hammer spring on his.
So, as others have said, if you can TRY ONE out, do it. These things are very subjective, and each of us is different. I really like the little gun, and think it is a hoot to shoot, but others have no use for it. As they say: "Different strokes for different folks".