I can only offer anecdotal comments.  Long time user of PitchFactor & H9s, with some A/B algorithm comparisons between the H90 & H9 alongside each other (but not all yet).  Many of the H9 algos have been tweaked; I believe the new SIFT tech has been applied to original H9 pitch algorithms.  I find effects like PitchFlex to be much more usable.  Diatonic & QuadraVox as well.  Then there’s the overall ‘better, cleaner, clearer’ I’m hearing, system-wide (subjectively).

System – Source Type has now been broken into Soprano / Alto / Tenor / Bass, for targeting the tracking / filters / tone controls to your instrument’s range.  Other than synthesized, I have tested any vocal or reed instruments through the H90.  But in theory, why not use the latest & greatest Polyphony algorithm for monophonic input?

The pitch shifting is right up there with the best currently out there.  And the Auto EQ parameter does well in preserving the formant of your instruments.  I haven’t had to adjust it off the default value of 10.   Again, based mainly on single note guitar input (heavily processed upstream, or squeaky clean).  I can’t project those results onto, say, your acoustic flute, though.