Lots of pros & cons and trains of thought. What's right for one family may be different than what's right for another or for you due to various things like vacation time, vacations at Disney vs. elsewhere, financial situation, booking/canceling on short notice, etc.
If you are consistently renting
DVC points, and you're planning many more trips for the future, then yes, you should probably buy. But know that it is a multi-year commitment until your break-even point vs renting.
Do a lot of research for which resorts you like, what their expiration date is, what the annual dues are (this is where the main long term expense lives!), points cost for the room types & views that you want, etc. Don't assume that you can always get the cheapest rooms & views at the times you need if you're scheduling around school breaks or holidays. Have a plan "B" just in case.
One of my pet peeves is that we call some of them the "2042" resorts because of their expiration year, but it is too easy to forget that 2041 is the last year you get points at those resorts, and those points have to be used by Jan 31, 2042. And similar for other resorts with later expiration dates.
And if looking at resale contracts, pay attention to whether they're "loaded" with current year points and maybe even banked points from the previous year, vs. "stripped" without current year points or next year's points. I would expect to pay a little more for a loaded contract, or a lot less for a stripped contract. Personally, I have zero interest in a stripped contract.
And Use Years; that's a long discussion too.