Aegir,
I love my Quatros. When I was trying to decide between them and the Volos, I thought I might use less air with the easier kicking volos. I was told the difference wouldn't be noticable, Also the Quatros should be better for short busts of speed ( to get to another diver quickly if neccesary ), Also The volos would not be practical with some kicks ( such as inside a wreck ) I don't have any wreck training yet but I was looking ahead.
My son Likes his volos, but hasn't had them in open water yet,( hes just pool training so far ) We'll be diving off of Grand Bahama in a couple of weeks and should get the chance to swap fins and check each others out.
I'll get back to you and let you know.
Tavi