I’ve found that the best way to look at exchanging is think of it like travel agencies – if they’ve sold all their space for a particular holiday you have to pick another, that’s life. Exchanging is kinda the same, if there is space available you can swap your timeshare for another, if there’s not space available at your first choice then you’ve simply got to pick another.
The rest depends on what you bought, where etc as @mayanjc says and that is designed to be fair to all members on a like for like basis – I guess this is the same as the old saying “you get what you pay for”, a better timeshare may well deliver better opportunities than another.
I am happily in my third year of ownership, and all in all love the concept.