Six is better than five and the GP100 is better than the awful SP101 (a gun that does just about everything wrong).
The larger frame GP100 is ... heavy enough to actually use, though the SP101 is no lightweight. Neither gun fits in the average pocket, though it'll fit in overalls.
So do you feel that the SP101 is too cramped for its caliber size or that too many corners are cut in production? Also, do you feel that while better than lighter J-Frame competitors, the SP101 is simply overwhelmed by .357 magnum? If so, do you think it would be a good fit for the lighter .327 magnum?