Regarding target wadcutter 148s in a snubbie: figure they'll do about 700fps. Total energy will be around 160ft/lbs.
In comparison, the 158+Ps should pull at least 200ft/lbs if doing a hair over 750fps, and will expand. And more like 800fps+ (230ish ft/lbs) isn't at all unlikely depending on your gun, cylinder gap, etc.
As someone else said, the 148 target wadcutters WILL penetrate skull, there's enough energy there to make it all the way through the sinus cavities if need be (which is suprisingly difficult and a reason why a lot of people survive mousegun headshots).
If you're recoil sensitive and can shoot the wadcutters VERY accurately, well, you're not unarmed with them. But for God's sake realize their limits: on a torso shot, they'll hurt but stopping power will be very minimal, the low velocity means only minor "shockwave effects" from that blunt nose.
As to the Nyclad version of the 158+P LSWC-HP, I'm not sure that would help, or hurt. They might go a bit faster, but the nylon coating might reduce the hollowpoint cavity volume in unacceptable ways. I figure the "plain lead" varieties such as the Winchester are the "time tested standard" and have thus far stayed with those. If you're pondering the Nyclads, compare the HP cavity in it to the plain lead equivelent, and make your choice.
Jim