I have stayed at MGV twice (including once last month) and unfortunately I don't know the building numbering well enough to give you advice on what to request, but I did want to pass along that I do think it's very important to request a specific building.
On my first trip about two years ago we were in what must have been a newly renovated unit and it was totally beautiful and flawless. Very nicely decorated, all furniture, linens, etc. seemed brand new and the unit was spotless. We were also very conveniently located to what was then the main pool (were still building the new one across the bridge) as well as the marketplace and other amenities so we used them all the time.
On my more recent trip, not so lucky. First was accidentally placed in a smoking unit. Although it appeared very nice and was an okay, but not great location, the smell was overpowering so I headed back to the front desk to wait in line again. Although I had requested a new or newly-refurbished unit, definitely got neither. Furniture was quite worn, unit needed painting, had old carpet and a fair number of bugs (although not totally avoidable in Orlando, particularly with doors opening to outside). It also seemed to be the very most distant building from both of the main pools and the marketplace and other amenities so we hardly used them.
Moral of the story is that MGV is actually a very nice resort with good amenities, but the actual units and desirability of location varies widely so it definitely pays to do your homework, make requests and make sure you get them.