I would agree with everyone here...
"Buy where you want to stay..."
That being said... A couple of other things to factor in...
Length of contracts:
VWL contracts will expire in 2042... SSR contracts expire in 2054.. If the 12 extra years are a big issue (and for many potentional buyers they are), then SSR is currently the only resort to offer them... (Eventually DVD will more than likely build other resorts with the longer contract scheme, and some have speculated that they may offer "contract extensions for those of us who purchased at the other resorts..)
Location:
You have already said that you'd like to be close to MK... SSR is across from DTD, and is a bit of a ride from MK...
Grand Villas:
SSR has Grand Villas, whereas VWL does not.
Community Hall:
SSR has a community hall, whereas VWL does not.
Size:
As was previously posted.. VWL is the smallest
DVC resort, and shares its accomidations and CM's with WL guests..
Room Layout:
While the differences between the VWL and SSR rooms are not as drastic as between OKW and BWV or BCV and Vero, there are some minor changes with the SSR Rooms... The two main things that come to mind are the bathroom layouts and where the adjoining door in the 2BR units are located.
Room Decor:
VWL and SSR both have dark stained trim and furniture, but the theming is quite different.