Here is the real low down.
Units: Sequel section is actually a little bigger in terms of SF, but you lose living space with the two entry ways. It makes the original side seem bigger and more open. Decor has been redone on both sides, and I wouldn't say that either is nicer than the other. The Original buildings are much nicer in terms of architecture, shrubs, grassy areas, and art work in the common building areas.
Location: Sequel is closer to the larger pool, tennis courts, and kids playground. Original is on the golf course and closer to the check in building with the indoor pool, Bistro, and sales center
Buildings: Sequel has three floors of long hallways with doors on either side. It gets noisy with foot traffic. Original, fewer units on each floor, elevator in the middle, more quiet.
Buildings on the Original side: If you want really big units, there is one building (Berkeley) that was build at condos prior to the purchase by Marriott. It isn't the same layout as the rest. Request that building and ask for the second or third floor. The third floor has two story units and two of them are 3BR. Otherwise you may want Chesapeake which is next to Berkeley and next to the main building; Governors is on the other side of the main building and has the activities center in the basement along with the laundry for all of the bedding and towels. Ask for a second floor unit facing the golf course in all of the buildings except for Berkeley or you may end up with a first floor unit facing the parking lot where your balcony isn't very private.
Balconies: they are screened in and have furniture.
Also, walk over to the Fords Colony Country Club and check it out. You get free golf greens fees if you are a Marriott owner. Their sports bar (Murdoch's) is open to the public and get 10% off, but can't charge to your room. The food is pretty good and inexpensive. October is probably the best weather month in Williamsburg.