I've had both, ended up selling both. They are quality pedals, no doubt about that (disclaimer: big MXR fan). The BT didn't sound very good as fuzz/distortion with the gear I had at the time, but I must admit that it worked well as mild to med OD. As for the SP, I loved its massive fuzzness, but it didn't sit well in the mix, even though I tweaked and tweaked. I was playing through two 15 inchers at the time, so that could've been part of the explanation, according to TBers.
Jazz 4 str. / Grind 5 str.>TU-2>Pigtronix BEP>BSW>LMB-3>BassDriver>Stereo Chorus> PBDDI>Fender Rumble 350 (PT-2/DC Brick/Planet Waves cables)