The older of the two resorts, Sheraton Vistana Resort, has been completely remodeled over the last year or so. Sheraon Vistana Villages is a new enough resort that any of the areas would be a nice enough place to stay. If you're doing a lot of Disney on your vacation, the Sheraton Vistana Resort is an ideal and very close location.
What would you consider bad? They are very similar, amenity wise. I am at Vistana Villages this week. The only thing I can see that may be a problem is that they are doing construction on the lot next to the resort. (Different company, I believe.) I haven't heard anything, but perhaps the building directly next to the fence might have an issue. The Resort is closer to Disney, but the Villages are probably only a mile or two further away, and it very easy drive (less than a mile?) to SeaWorld. I haven't had any trouble parking right outside the building yet.
What would you consider bad?
Are the barbeque grills working at VV? We've stayed at VV several years in a row in May and last year it was hard to find one that worked. We're staying at VR for the first time this May and are looking forward to it. VR is a lot closer to Disney but both resorts are well located.
Two summers ago I stayed at one of the first sections that had been redone. The BBQ Grills were charcoal. Not sure if they have been replaced since. If not, make sure you buy your charcoal off property as they were charging $20.00 for a small bag
June of 2012 they were all gas, and it was a struggle to find one that would light at all.