There are two.. Vistana Villages on I-Drive and Vistana Resort on 535 -
We have stayed at both. At both you can get a 2 bedroom Condo with full kitchen and washer/dryer etc. In general the Villages is a newer resort. We did not like Vistana Resort as we were in a horrible old Condo (c1982 and never re-decorated!) and despite asking to be close to the pool, they actually could not have put us further away if they tried. Plus I found the staff rude.. the resort was empty and they absolutely refused to move us.
That apart.. its a nice resort..
Vistana Villages is newer and so, you wont get a horrible apartment! Both have similar facilities. Villages is smaller, so you will be potentially closer to the pool, but Vistana Resort has more pools..
I would go back to the Villages, but not to Vistana unless they could guarantee that I got a newer apartment (which they wont, so I wont go back!)
Hope that helps!