Just to add my comments....
We started going to ' EuroDisney ' now known as Disneyland Paris when it opened in 1992, with only one park. ( similar to the Magic Kingdom park in WDW ). Our boys loved it as they could divide time between the hotel pools and the park. We stayed every summer for 5 or 7 days.
The Studios Park was added in 2002, and is still expanding, with the latest addition of Toy Story Playland and a new indoor Ratatouille ride is planned next.
You cannot compare WDW/ Orlando holiday with a short break to DLP as they are both completely different types of holiday.
WDW had 4 Disney parks and two waterparks. Then you also have Universal Studios park, Islands of Adventure, SeaWorld, Aquatica waterpark, the Space Centre, Busch Gardens ( Tampa ), Discovery Cove, and other trips like airboat rides through the Everglades, Swamp Buggy rides through a Semisole Indian Reservation, cruise boat trips to the gulf of Mexico....the list goes on....
We went to Florida for the first time when our boys were 9 and 13, which was fine apart from DS2 being too small for some rides like coasters. He was not that keen to try them anyway, so didn't get upset seeing his brother ride with us in turn, using childswop.
It was a very busy and tiring two weeks, staying in the cheapest Disney hotel, which had just opened. ( All Star Movies ). We used the Disney buses, and taxis to visit parks outside Disneyworld resort.
Two years later DS2 was getting braver, but still too small for some rides at 11yrs. By 2005 when he was 14 he could now go on everything.
Space Mountain in WDW is nothing like Space Mountain in DLP. The ride in DLP is far more extreme with a minimum height of 1.32m. It is more like Rock n Roller Coaster.
We have been to Orlando / WDW 5 times now, and have done something different on each trip. Last time we did Discovery Cove, which was expensive, but a lovely day.
DS1 really enjoyed the Space Centre, but DS2 got bored with some of it.
Both boys really enjoyed the airboat ride through the Everglades and swamp buggy ride through the Indian reservation, ending with a short cruise, but it was a very long day with an early start and a lot of driving. We booked this as an excursion leaving from our Disney hotel.
We have always had between 14 and 18 nts holidays there, to manage to do most things with rest days in waterparks as well.
Timing your trip is very important to avoid crowds and long queues - avoid American school and college holidays.
We still visit DLP regularly as well - at least twice a year, for 3-5 days usually. The different seasons vary enormously there, so again you have to pick the right time for your family. Most people who have planned well, and got lots of info from the DLP forums on Trip Advisor or other DLP sites have had a great time. The bad reviews are usually because people expected it to be like America, or did no planning, or went at the wrong time, which makes me feel very sad.
There is no point in grumbling there were no fireworks or electrical parade if you don't check when they are on before booking!
There are some great rides and attractions in DLP that they do not have in American parks, and some rides are better as DLP was built later, so they improved them.
WDW and DLP are both worth visiting, but one is a major holiday and one is a short break, with the opportunity to visit Paris as well. ( we usually have one day sightseeing in Paris, which is only 40 mins on the train from Disney ).
Next year we are going to Disneyland California for the first time as part of a West coast trip, and I am sure that will be very different as well.
Whatever you do - Have a Magical Time!