dp, I'm afraid it's WAY more complicated than just the bullet weights. Velocity and particularly bullet configuration count more.
158 grain, long the standard .38 Special weight, was only available in round-nose solid configuration for 60 or so years. During that time it earned a reputation for impotence. The first starkly improved load was the 110 grain Super Vel, which worked better because it had an expanding bullet configuration (semi-jacketed hollow point) and moved way faster than the load that preceded it.
Back in the 1970s, the 158 grain came back to the forefront, but with an all-lead hollow point configuration and loaded to +P velocity, and this quickly took the lead. From Chicago to Dade County and Miami, Florida, and elsewhere, this earned a rep as the best of the .38 Special service revolver loads. FBI and DEA adopted it, too.
Today, we have something at least slightly better for shorter barrel guns like your SP101: Speer's 135 grain Gold Dot +P. It seems to be THE top load for the snub .38 today, and does pretty darn good out of longer barrels, too.
Hoping this has been helpful,
Last edited by Mas Ayoob; 09-11-2012 at 21:04..