Betsy, I have owned DVC in the past and currently own Fairfield points. There don't seem to be many others with ownership experience with both companies' points programs here. There are a handful of DVC members who post to the Yahoo Fairfield_Timeshare group. I would encourage you to try posting there as well, for comparisons.
The DVC program is more flexible overall. The Fairfield program offers far more resort destinations and their newest resorts are truly Gold Crown.
Customer service is excellent with DVC, variable with FF. Having learned the FF system, I am able to get excellent customer service there as well and it is steadily improving, IMHO, thankfully. It does take a while to know what you are doing, so that you can ask the right questions and learn to secure what you want. It's not as easy as DVC.
There are definitely some restrictions on prime season travel to most FF destinations. Everyone wants to travel then and the premium on points usage is not as vast as it is with DVC, encouraging more requests for usage during primetime. Therefore, primetime at FF prime resorts books more solidly. Early planning may be more important with FF.
We have thoroughly enjoyed our points ownership with FF. We spent a couple, very pleasant midweek short stays at the FF Smoky Mountains resort in Sept & Dec. We just returned yesterday from a 5 night stay near Washington DC at FF Alexandria, an urban resort that compared quite well with The Manhattan Club (which we've traded into in the past via RCI, using our FF points).
We like the RCI trading options and the ability to secure upgrades via RCI. For me, that's part of the flexibility advantage of FF. Other FF owners (who own at II home resorts) have recently posted about their secured exchanges into DVC for Aug/Sept 2003, including unit size upgrades.
Again, understanding the system is important, to make the most of it. We now know when we can reasonably expect to secure our short stay reservations and how to get the tougher ones. We know how to handle major holidays and primetime. And we tend to travel just offseason anyway, so we always tend to get what we want.
OTOH, newbies are easily frustrated with FF, understandably. And the terrible sales practices of their sales staff make this much worse, IMHO. These things don't happen very often with DVC, so the edge goes easily to DVC, in this regard. Bottom line is, there are advantages to both. Whether it's worthwhile to you will depend upon your vacation "wants" and whether they are achievable via FF or not. For us, FF is an excellent choice! HTH.