The main difference between RCI and DAE is that DAE do not do like-for-like exchanges. Every week deposited has the same trading power (but see 2nd paragraph). This means that a studio in Tenerife in early December is capable of pulling a peak summer holiday, 2 or 3 bedroom unit somewhere else. Therefore, there are a lot more out-of-season studios in obscure resorts available than big units at Marriott's or Disney.
But, if you do deposit a 2 bedroom or bigger unit in a peak holiday week (refer to their website for details) you get TWO weeks credit instead of one. This year, my August Loch Rannoch week has pulled two weeks in 2-bedroom units in July at Macdonalds Doña Lola and Pueblo Evita, on the Costa del Sol. Really, not too bad at all!
You don't have to deposit anything with DAE to join. If you are a timeshare owner, you can join, without paying anything, if you don't want. Even if you don't intend to use DAE for exchanges, you'll have access to the bonus weeks - some as cheap as 79 quid - for late-booking holidays.
Everything is very transparent with DAE - you can see what is available, through their website - even if you're not a member. RCI only shows the availability after you've deposited a week.
But, if you do have an in-demand week at a high quality resort, you might find you get a better quality of exchange through RCI. I know you do through Interval International, as I'm a member of that too.
And, if you like a points-based system, look at Redweek.com exchange, which uses a lot of DAE inventory, so it's like DAE Points. I managed to get two weeks of holidays (one last August and again this easter) in exchange for a week which wouldn't have got more than one week from DAE and has poor trading power with RCI.