We trade our other (resale) timeshares into DVC and we use our Wyndham (resale) points to reserve nightly stays at Bonnet Creek and other Wyndhams. Both are generally less expensive for us than renting from other owners/members or buying from the developers. But for a newbie to start to do this, they either need to get in through an experienced timesharer's resales (tried and true trade weeks) or take the time to learn a lot on TUG or TS4Ms or similar forums. It's very easy to waste your money buying something that won't do what you intend.
To the OP: We much prefer the Wyndham Bonnet Creek Resort over Sheraton Vistana Villages, especially if you'll be spending most of your time at the Disney venues and/or if you'll have a wide range of ages and kids in your party. It's nice to have the extra transportation options to the parks too - if you won't have a car or enough cars while staying offsite, it's the next best thing to Disney's shuttles.
But if you'll be spending a fair amount of time at Sea World, other area attractions and offsite restaurants, and if you love a pretty waterfall pool and you'll be traveling with adults, I think the Sheraton is a bit more romantic and its location, further from Disney, would not matter so much.
