It hinges on your opportunity cost figure. You can pick one to more or less justify any decision you want. But, once you have a figure you can live with, roll in depreciation, and use the total figure for the per-year costs of the purchase price, adding in dues. That gives you your annual cost per point in present-year dollars.
I use 7% for depreciation and opportunity---probably a little high in the current economic climate, but as you say, it's a long-term purchase. At that level, a $60 SSR resale point is $8.86 ($4.46 in dues, $4.20 in carrying costs on the purchase), which is cheaper than renting ($10). An AKV point from the developer at $96, though, is $11.67 under the same assumptions---more expensive than renting.
You could try to roll it forward under various assumptions about rental rate vs. dues increases, but then you just make up more numbers on those rates, giving you even more opportunity to come to whichever conclusion you'd like to justify.
At the end of the day, the numbers are close enough that I'd decide based on whether I wanted control and a long-term association, or the flexibility to skip
DVC and look elsewhere for vacations down the road as my kids got older or my tastes changed.
The numbers in her examples are a little dated, but the idea still works.
