My personal preference at this point in time is to belong to a timeshare system that has it's own internal exchange program. There are many out there and more companies seem to be joining the concept of self contained exchange programs each year. All have different rules for their internal programs so it might take you some time to weed through them to see which ones fit your needs. At issue for some is that if you buy resale, you don't get to participate in their internal exchange program without paying a fee or having to buy something from them direct at inflated prices.
We own in two points based systems, both of which work very well for our needs. One is DRI (Diamond Resrots International) and the other is Hilton Grand Vacation Club.
Of the two, DRI has more resorts in more locations. DRI is trying to get all of the resorts they manage to one comparable level. In doing so, MF's at some of the resorts have sky rocketed from previous level. Still, with the correct number of points we can travel to all of the popular destinations including Hawaii without to much effort. DRI does not allow resale weeks to participate in their internal points program without either paying a large joiner fee or buying something from them directly. Recently it appears they've done away with the joiner fee and require a direct purchase, which will cost you several thousand dollars in addition to any week you might buy on the resale market.
HGVC has great resorts and a very easy to understand internal points program and is very flexible. HGVC also does not discriminate against resale buyers. Resale buyers have all the same rights as those who buy direct with one exception that I know of. That exception is that points bought resale don't qualify for credit towards elite status. The problem with HGVC is their resorts are concentrated in Orlando, Vegas and Hawaii. They do have several affiliated resorts in Florida, a few overseas, one in New York and one in Colorado but, their locations are limited. That means you have to use your HGVC points to exchange through RCI if you want to go anywhere other than those few HGVC locations.
Advantages of internal points based programs are that you can avoid the external exchange companies like RCI and Interval. This might lower your annual costs for usage depending on how the progams are set up and how many exchanges you make per year. If each internal exchange you make does not incure a fee or, incures a smaller fee than what either RCI or I.I. charges, there are some savings.
Internal programs tend to be easier to make exchanges IMHO than going though an external exchange company. The rules and values typically remain the same. With either Interval or RCI points required or the value of your points can change. Interval does not have it's own points program but, it does have programs where companies that do have points programs can allow their owners to trade via points rather than having to reserve and deposit.
The big disadvantage I'm starting to see is that some companies are using points based exchange programs as a way to exclude resale buyers. This hurts those who might want to sell their ownership down the road by de-valuing those programs on the resale market. There is a HUGE thread about Marriott's probability of entering the points based internal exchange game. The rumor is that those who have bought direct from Marriott will be happy but those who bought resale will be sorry they didn't buy direct. Until we actually see the program, it's hard to tell who will be happy and who won't. But that's the power of internal programs. Developers can make rules that inhibit resale purchasers and discourage resale transactions.