I feel vari audio has the edge with pitch and stretch quality on vocal, but flex pitch seems to work better on more sources, like mono instruments as well.
Overall, after now using it for the week, I believe it's as good as melodyne, honest.
I have melodyne editor and use it in s1 and compared it head to head, and I feel logic has even better integration than celemonys ARA, so I understand why apple did it their own way.
Plus, apple have a patent already for polyphonic and word is its coming.
I'd still keep melodyne around for when I use studio one