Been to both and love them both for different reasons. I'll try and compare some of the attractions for you.
Big thunder mountain - much better in Paris - it goes under the river first!
Phantom Manor - different story to Haunted Mansion, spookier but less high tech
Pirates of the carribean - No Jack Sparrow, but the ride is longer and more intense
Fantasyland rides are pretty similar
Space Mountain - Inversion coaster very intense - can bang your head a bit
Star Tours - old version
Buzz is the same
There are different attractions in the Studios - Crush's Coaster and Toy Story Playland well worth a visit.
Tower of Terror - no forward ride into twighlight zone, but very intense
Rock n Roller - Similar with different storyline at the beginning
Dreams is amazing - A must see!
If staying on site it is great to be able to walk from hotels through the village to the parks, everything is really close.
Restaurants - not as well themed and service is much slower, but still some nice choices
I'm sure with a bit of planning and taking advantage of Extra Magic hours if you can you'll have a great time!
