When I get a chance I'll get you a link to a record wholly recorded with the same idea. If ya don't see it soon enough, give me a nudge. It's a trio, but we performed the same stuff as a duo too. Micro POG, though I haven't tried the 2, from what I hear it tracks as well if not better, and the octave up isn't as digital sounding. I've tried a handful of others and it really comes down to what timbre you like, how it handles the transient attack and to a minor degree how it tracks. Though most of the better ones are pretty much all on par for tracking.
What you feed it, how you shape it afterward, and what amp it goes into means a heaping ton to the tone and natural sound of it.