The SY1000 is known to have poor guitar P2M tracking. That's not just my opinion but also the opinion of many experienced users on vguitarforums.SY and GP-10 were both far superior for pitch to MIDI than any previous Roland unit I had.
I would like to have improved guitar P2M ( flawless) but haven't heard good things about the GM800 in that reguards and was wondering if you had a chance to test it.The GM-800 has a better edge on those for tracking accuracy, not tried the guitar to mid on the GM-800 as there has been no need to since the GM has the Zen Core engine which contains every synth type Roland has made, including the L.A. synth from the GR-50 and the D series synths, and if the synth model or wavetable is not there, you can load up new ones with expansion packs.
My interest is with midi guitar triggering of a bunch of analog synths and assorted PCM based Rompers that I own. The internal sounds in the GR50 trigger well but never really sounded that great.