There are many differences between resorts and between WDW resorts and the off property DVC. You do want to consider many aspects of owning DVC -- some questions to think about are:
Where will you visit the majority of the time? If you answered at WDW then you at least want to buy a WDW property
Look at the Maintenance fees- Vero and HHI both have the highest MF, being on the coast also puts it at a higher risk for special assessments for storm damage
How old will you be in 15 years? The reason to consider this is that those 2 properties both have early expiration which means that if you were to only hold on to the contract for 10-15 years and then turn around to sell it those resorts with longer expiration will be worth more having more years left. That may or may not sway some people. But if you are fairly young say in your 30's and you buy an early expiration -- it will be done and you will only be in your 50's. I myself at least wanted a longer contract to make sure i get full use well into my retirement or at least would be able to sell it and recoup some $$.
It is getting more and more difficult to book at 7 months so buying where you don't mind staying is almost essential. How disappointing would it be to say you want to spend any time between Oct and Jan at WDW, but it is fully booked up with all those who own on property.
Some options would be if you really like HHI to buy a smaller contract there and then a smaller contract on property - this way you have some flexibility in your planning/booking. I considered a HHI contract (as we do want to vacation there aside from our AK contract) but some wiser members here opened my eye to the fact that other properties at HHI whether it be private residences, condos/timeshares are much less expensive than owning at HHI DVC.