I'm using both Kagu and Canola. In the car i has to be Canola as it is thumb friendly if a little awkward to navigate.

Kagu has some coolness (like scrolling and a much easier to use seek).

All of them lack bookmarking (which IMHO is crucial with any player - audio books and podcasts are a pain without).

UKMP - never liked it too much. UKTube works well but is clunky. UKMP interface just too hard to use with a thumb fullstop.