If you buy 250 points @ $20 less per point, you will save $5,000 on your initial investment. That's $135 per year for the 37 years you are buying. I'm not sure what the maintenance is at Beach Club, but I know VB is currently $4.87. If it's 50 cents less, as Tammy said, that would be $125 a year more. If those numbers are accurate, there's really not much difference in the total cost.
I would base my decision on where and when I wanted to stay. If you want to go to Vero in the summer, definitely buy Vero. If you want to go to BCV during Food & Wine in October, you're going to have difficulty getting what you want without owning there.
But...if you want to go to BCV in February, you'll probably be fine with the seven-month window. Or, if your family can't make final decisions and book more than seven months out, you aren't really gaining much with ownership at a specific resort.