I would look at the overall cost when you factor in annual dues. The dues on 50 VGF points is going to hurt a lot less than dues on 150 SSR points. But that’s not the only consideration.
You’re also going to pay a premium price for that small VGF contract. Much more $/pt. than a 150-point contract at VGF. And buying VGF @50 points is not going to get you 3 nights in a VGF studio every year during most seasons. The cheapest season for 2021 is 9/01-09/19 where a standard view studio is 16 pts. per night, Sun-Thurs.
Consider how many points you would actually use and look for a contract that suits your needs. Purchasing 150 SSR points may be way more points than you need every year, considering that you already have contracts at 2 other resorts. Do you really want to buy that many, knowing that you will have to pay annual dues on them?
My advice would be to get the number of SSR points that you will need and seek a transfer of VGF points when you wish to stay there.