The main pool at WL has a slide (but I believe it is down for maintanance right now). It is not anything huge and since I have not been to OKW, I don't know how it compares.
At OKW, you not only get that main feature pool, but also three additional pool/hot tub/play areas (Miller's Road, Turtle Pond, and South Point). At VWL, you will get one additional pool besides the feature one.