In my opinion the Polo STD is the ultimate low wind kite. I prefer this one above the Zen.
The Revolution (Barresi or Pro) STD's windrange lies a bit more shifted to the upper part of the windrange.
So.. Polo starts earlier, Rev B or Pro flies better in the higher windrange (for the STD).
I have got the feeling the Polo is feeling a bit twitchy/nervous in higher winds (more than the Rev.)
Solution: i fly my Polo VTD when the wind picks up !