Yes, Rob is 100% right (as usual ). In a way, it is surprising they made the name so similar, although it is possible to say that by adding the Walt to the Disney Studios they underlined the difference
Rock n Roller is virtually identical in terms of the track but is still different in terms of the pre-show (different scenario with Aerosmith) and the lighting package, while the WDS tram tour adds sections from the TV series Dinotopia (a small scenery setpiece) and the film Reign of Fire (complete with very realistic dragon's breath!). There is also a copy of the Magic Carpets ride from WDW's Magic Kingdom, but essentially this is a very different park that is well worth seeing in its own right (even though it is only about 70% completed, IMHO).
I totally agree about WDS being only 70% complete.
IMO R'n'R is much better at Disney Studios Paris - I thought the layout and length was much better.
The stunt show in Paris is exceptional and beats MGM's Indiana Jones attraction hands down.
Hopefully some more attractions will be added to try and complete the park, as IMO it is wonderfully set out (The Studio 1 bit near the entrance with the shops/restaurants and band- all undercover is a great idea) and everything is within short walking distance.