We have stayed at both. WL is my favorite resort. The building is amazing! The lobby is to die for. There are rocking chairs all around & lots of little nooks to relax in! The pool is nice with waterfalls and such. Downside is bus transportation.(I heard they may change this soon), but I believe you still share a bus with Poly & GF to get to some parks. The rooms aren't very large, but they do have bunkbed rooms which my kids love.
I loved the Contemporary, too. The rooms were very large. 2 queens beds & a daybed. Bathroom is a lot larger,too. I like the Contemporary food court better than WL. If you like to use the monorail, this is the resort for you. The pool is very plain, but my kids loved it because the slide is very good.
Have a great trip!