I would say that I get 10 to 1 (VRBO to HomeAway). I'm on the west coast. I do advertise on both since I do get at least 2 bookings per year from HomeAway that I probably wouldn't have gotten on VRBO unless they are looking at both sites.
Which service is best for you really depends which service is doing best for Google searches in your area.
Here is my post on how to use Google (or any other search engine, although Google is by far the most important) to figure out which service (HomeAway, VRBO, VacationHomeRentals, TripKey, etc) is best for you: