Most SP101s I have handled have had heavier double action triggers than GP100s, but this is a generalization.
I have owned both but no longer have an SP101. It was great (and well-built), but I couldn't shoot it as well as the GP100. I find I shoot a full-size revolver best. If an SP101 came along at the right price, I wouldn't hesitate to own another. I like those new 4" ones with adjustable sights. Maybe there are oversize grips for them to make them handle more like a full-size revolver.