The .357 mag from a short barrel will still have a velocity/energy edge over the .38 +P from the same barrel. This assumes all else being equal. A .38 +P has less velocity from a snubby than from a four-plus-inch barrel, too. The decision to make is whether one can control the magnums, and will place shots well enough, or even wants to go to the trouble. There is no shame in making an informed decision; guys with far more testosterone than me have elected to stay with milder stuff, and go for precision.
A colleague who works with a west coast PD, and is widely respected as a law enforcement trainer, who posts on another forum as "nyeti," has called the snubby .357, and the SP101 in particular, a "hand-held flash bang." He believes that some of the legendary stopping power of the .357 in close-range defensive shootings derives from the fact that it can be very difficult to press an attack when suddenly faced with the stunning effect from the bright flash and loud noise, coupled with a medium-caliber hole leaking bodily fluids. Makes sense to me; no matter how much the shooter is affected by the sound and fury, the guy downrange is feeling it much more. (The weapon itself shades the shooter from the brightest central part of the flash, of course.)
It took me a while to adjust to the .357 in the SP101, and I still carry magnums in my little Rugers, but as I enter my late 40's, I don't shoot as many full-pressure rounds anymore, and am more likely to carry slightly milder stuff, such as Winchester 145-grain Silvertips in my lighter .357 weapons, such as the SP101 and Speed Six, saving the to-the-firewall 125-grain Federals for the 4" and 6" GP100s.
Keep in mind the role of the particular weapon. If I pull a .357 SP101, it will likely be a close-range face-to-face incident, over very quickly. If I am responding to an incident from a distance, or anticipating an armed encounter, I will choose a service-style handgun and/or long weapon, with the snubby relegated to backup status, or perhaps not even brought along for the ride. Two P229 pistols (my personally-owned duty pistols) make great back-up for a shotgun or rifle!