Well, there are a number of variables on both sides so no easy, simple answer,
@SwanVT2. Often it is not less expensive for a Fort stay.
On the DVC rental side, it's cost per point and what size/where you stay? Studio or larger? OKW or BLT? Can you actually GET the points you want for the date/place?
On the Fort side, there are also a variety of campsite levels and thus prices. Often the middle 3 tiers fill first (Full, Preferred, Premium) leaving only the most expensive (Premium Meadows) or the least expensive (Tent). Even those eventually fill for all but the least busy times. The camper/rv you rent depends on the size/vendor and also length of stay. A 4-night rental on a per night basis is often more expensive than a 7-night rental plus consider add-ons like delivery charges (if any).
Can you actually GET the Fort nights at the level you want? Have you yet? You could do a room-only reservation and cancel later on and get your deposit back if you decide to to DVC.
There is a train of thought out there that camping is a cheap way to visit WDW and stay on property (and I'm not suggesting this about you). I suppose if one stays in a tent and can guarantee great weather, that's true. But the more common reality is that the truck/trailer combo or drive-able rv are the way we Fort folks go and that requires QUITE an upfront investment that you don't have to match in the hotel/DVC rental equation. Thus, I'd suggest we make the investment up front because that's the way we prefer to travel and vacation over a period of months/years. Closer to nature and sleep in our own beds away from home. The vendor makes that investment for you on a rental and you put the site with it.
You get a kitchen in either case so it's common to both to be able to eat a meal "in" rather than having to go out to Counter or Table service most times.
Let us know what you decide and why, please. That will help the next person in your shoes understand better. And can you let us know how many people in your party and when you are looking to travel?
Good luck!
Bama Ed
PS - also the dirty (not so) secret about Fort Wilderness campsite prices is that they haven't added new campsites since the mid-1970s to meet growing demand. More rv/camper sales, baby boomers retiring, etc. But DVC has grown to meet demand. So the Fort has had the same number of sites for decades but more demand over the years - and the price goes up as a result.