I'd agree with Telerocker. I'd use a different word than softer, though: I'd say Stormies are a tad sweeter sounding. (But softer is equally true!)
I've got both and reckon you'd love either. Both would be fine for the type of music that you play. And, actually, Riff Raffs would be OK too

- I've got Riff Raffs in one SG, Stormies in another, Mules in a 335 (were in an LP), and Stormies in two LPs. (I haven't tried Mules in an SG myself, but as long as the SG isn't too "middy" acoustically I think they'd be fine).
They can all cover each other's tones. For example, if you are familiar with the album, any of the three pickups can easily do
all of the sounds from both Duane and Dicky on the Allman Brothers at the Fillmore. Another example, my stormy SG, in my hands, seems to do a much better "Angus tone" than my riff raff SG does.
But, although they can easily cover each other's areas, each of the three excels at slightly different different things. I'd say: if, overall, you lean more towards sweeter "PAF" sounds, and use that most of the time, go for stormies. If you want a raunchy/grittier "PAF" sound more of the time, go for mules. If you value a harder, more focused, "PAF" crunch when you need it, choose riff raffs.
Personally, I find Stormies the most versatile (of stormy/mule/riffraff), and they excel at the "PAF" sound that was always in my head - that's why I have so many sets of them - but I think you'd love all three.