The thread seems to have gone a little off track, but let me get this....you have a std SP rear shock and a Maxton rear shock and you want to know which one to keep?

Is the Maxton shock a re-worked SP unit or is it been built by Maxton? In both cases I would have assumed that the Maxton unit is going to be better that the SP unit, otherwise they wouldn't really be doing their job.

I had a re-valved Maxton shock on my MC18 about 10 years ago and it was great......though to be fair the original shock was about as much use as the springs in my Ikea sofa.

So sell the SP unit and bask in the knowledge that you've a trick little springer to show your mates down the pub.....even if it's purple!