The two Marriott resorts are about 5 miles apart so they're both close to Disney but you're right that Sabal Palms at the Marriott World Center is very close to Disney property.
Both are nice timeshares. Though, in my opinion, Grande Vista is the nicer resort of the two - lots more in terms of amenities, all of the childrens' activities programs are located right at the resort as opposed to the same type of activities being parceled out between the three resorts on Marriott World Center property, a bar/grill and a sit down restaurant at Grande Vista vs. food court at the hotel next to Sabal Palms, several varied pools at GV while one at Sabal, full resort store at GV while nothing right at Sabal (stores at the hotel and an express version store at the Royal Palms resort that's nearby), Sabal is much smaller than Grande Vista (which might or might not be a plus for you) and with slightly larger (I think) villas - all with their own entries from the parking spaces that are right in front of the villas. Sabal was refurbished a few years ago and Grande Vista is currently undergoing a refurbishment that will bring the villas up to a more recent version of the Marriott Vacation Club standard. We've enjoyed both resorts but prefer Grande Vista.
Both have their distinct benefits. If you want a quieter, slower paced resort then pick Sabal; and if you want a full resort feel with lots of on-site amenities (or plan to play golf) then choose Grande Vista. Given just the fact that both would be the same price I would would pick Grande Vista but I'd not be disappointed with Sabal either.
Dick Taylor