We've visited both several times each and really enjoyed them, though the vacation experience is very different from one to the other. I'm sure it's personal preference, but, to us:
Both have beach equipment rentals and beautiful beaches that stretch for miles. HH has a more level beach. At VB you're right on the beach (especially if you rent a beach cottage) and at HH you might have a view of the marsh from your villa but you need to take the shuttle that runs every 30 minutes or walk a couple miles to get to the beach house. The pool at VB feels larger.
VB resort is not close to much of anything (20 minute drive to restaurants downtown), more peaceful, and has more space overall, especially including the recreation area across the street. HH is right in the middle of things and feels a lot smaller but the villas are in smaller buildings and are more spaced out. Parking can be tight at HH.
We think the biking at HH is treacherous with all the traffic there, it's nice at VB but the number of potential bike routes is more limited.
The picnic spots and grills are limited at VB (at the north end near the campfire pit) and don't have a view. But, there are several public picnic spots on the islands on the Indian River that are right on the water and have really nice views, only a 2 minute drive from the VB resort. The picnic spots at HH are more plentiful and scattered about and most have a nice view of the marsh.
I don't have recent activity lists of both to factually compare, but, it felt like there were more activities offered at VB.
And finally, both have Dole Whips

, though HH has them only at the beach house.
You should have a great time at either resort. Have fun choosing and have fun on the trip!