All the parks are great, our favorite is Epcot. Stay away from Downtown Disney, as it is under reconstruction. I have been going to Disney since '79, after the first 3-4 visits, we were able to get down to 1 day per park, as we went to the NEW attractions, and a few of our favorites.
I agree with many of the above posts, especially 1 day is a short amount of time.
You will be doing LOTS of walking, wear comfortable shoes/sneakers.
If you can swing it, I suggest a mid week package, 3 or 4 days, staying in the park. This gets you a LOT of benefits, including early access to one park per day.
Hope this helps.
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Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
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