I know we are pretty biased toward HHI since it is our home resort. I even created this site to show it off:
http://web.me.com/apulk/DVC_HHI_Site_/Welcome.html
We stayed at Vero once as part of a WDW & beach trip. Now, the weather was terrible -- very cool for June and rain. We had it booked for 5 nights but actually ended up leaving after 2 nights and went back to WDW. The Vero resort is great -- love that it is all oceanfront. It also feels very remote (at least compared to the craziness of the Orlando area). Pool, rooms, main resort all very nice. But very different from HHI.
Beaches are very different -- lots more room on HHI, but you do either need to bike, drive or shuttle to the beach house. Tons of restaurants on HHI so the resort doesn't need a sit down place. Great place to ride bikes. I think
DVC HHI has more resort grounds too so there are more places to find a hammock, walk, explore.
For us, coming from the North, HHI is also more convenient in that you can either hit it "on the way" there or back. We are doing it again this summer...we'll stay Sunday thru Friday at DVC HHI then drive to WDW for 4 nights.