Hi Sherry:
I have an old Roland GK1 with a GK2 pickup mounted on an old Squier electric guitar. Roland had newer since I got my rig but I was happy with mine (and I didn't have the money to upgrade).
The sensitivity and innability to filter out 'artifacts' (when I pressed a string at the fret it might trigger a midi event even without plucking - but it's called a phantom note because it is only a few ticks long and easy to delete from the file using a sequencer.
I can set it up to record the individual strings on a seperate track (midi channel) so the tracks from one to six carries the nots respectively from each string.
Pitch bend (PB) is read by string as well. Any track with unesential pitch bends are seperated in the sequencer and the PB's are deleted from those tracks leaving only the essential string PB's. If you record all on one track, then do a PB on one string ALL strings will act on the PB - yuck.
I have done live performances with it with these results:
1- The phantom notes sound making me sound like Les Paul
2 Sometimes the phantom note is not the correct sound because it may pickup my finger touching at a fret other than the target - owww
3- I have assigned the two lowest strings E and A to a bass in the sequencer and then my thumb picking had better be right on. The different instrument sound stands out.
4- I'm a picker by habit and my old fingers don't always finger AT the fret anymore so I may get additional artifacts or phantoms.
With practice, the thing does a good job.
There are some dedicated guitars out there, notably the Godin and they make recording to midi pretty easy.
Keyboards are generally note-on, note off instruments with wheel (pitch bend)capabilities. A midi guitar is constantly in pitchbend (unless shut off in the converter module, which is a whole 'nother issue for sound reproduction) and needs to do a lot of work. It is like working with a fretless bass. The better you manage the fretboard the cleaner intonation and correctness of pitch you get. The midi guitar is sometimes like fretless because often the strings are pushed slightly across the fretboard even with near precise fingering. Not noticable in performance without a midi rig, but the pickup slightly exagerates them.
Hope this brief overview helps.
Larry