The 357 SuperMag is LONGER than the 357 Maximum, it's the 360 Dan Wesson that's shorter.
The 357 SuperMag was the first of the three.
The 357 Maximum was a commercial knock off of the the 357 SuperMag, Ruger did not want to make the frame window long enough to accomodate the 357 SuperMag.
The 360 Dan Wesson is shorter than either, being intended for the standard length DW karge frame.
The Dan Wesson 357 SuperMag is actually chambered for the 357 SuperMag, not withstanding the fact that the shroud will be marked 357 Maximum.
Get some loading data for the 357 SuperMag. It will do better than the 357 maximum, particularly with heavy bullets.