Parallel - more transparent, open sounding than series. Like a Stingray but with a little extra grind due to the ceramic pickup and voicing of the preamp
Single coil - more focused, thinner sounding, actually found the more I used this the more I liked it.
Series - biggest sounding of the three with more low mids? Just never felt it worked for me as such because the almost smiley face EQ curve in the parallel setting was what I liked about musicman from the off. Deep bottom with almost clicky top π
All of the above goes for the Stingray 5. Old habits die hard.