Lots of tradeoffs here and different things to consider. Will you ever need a larger room for a special trip to bring family? Will you get spoiled with some pixie dust and get upgraded to a 1BR and then want to stay in those?
If a large outlay today won't have a huge impact on your life/finances and you have considered the dues +increases for the next few decades and that doesn't cause any alarm, then a large purchase of direct points at a few resorts would be best. It will just make it easy. You also have to gamble with the cost/benefit of the resorts and consider that some have much easier to book at 7 months history and higher
point charts. As an example, my very uneducated guess is that Poly Tower will be fairly easy to book with some flexibility at 7 months due to it's aggressive classification of just about everything if you can even see a single inch of the park as park view.
Will you ever want to make it west in the 40 years? Owning at
Disneyland is likely more important than WDW if you want to go there with some frequency.
DVC is just a much smaller thing with Grand Cal very hard to book.
The other wildcard here is you can try and bundle a purchase and ask for a deal if the promos are similar (likely having to take the worst deal of the 2 (or 3) resorts. Very often there will be breakpoints for the purchase of 300 or even 500 points where the discounts can become fairly strong and I'd consider targeting one of those deals if you are going to buy a lot of points.
Good luck!