I'm new to these bikes, so please feel free to verify anything I say.
I've read, and been told, that they are different. The SP-1s were 2mm larger at the caliper and the master cylinder. The front rotors are also 0.5mm thinner on the SP-1s.
Is the SP-1 better? Doubt it for an average rider, one can argue the SP-1 is superior from a braking power standpoint. The SP-2s were basically SP-1s with all the revisions learned racing the SP-1s. In the end this might be a difference without a distinction for most riders. Unless you are used to pushing limits on the front brakes going into turns and can feel the feedback at the lever, doubt most of us mere mortal riders will be able to tell.
That said, I'm planning to upgrade my master cylinders in the hopes feeling the feedback more. I have an SP-1, so I'm going with a 19mm master.
Just my 2 cents, which is about what it might be worth.
2004 BMW R1150SR Project Touring Bike (in-work)
2005 Honda RC-51 SP-2 - future track tool
2014 Ducati HyperProject (Hyperstrada)
Last edited by BadToTheBown; 01-01-2016 at 12:37 PM.