Having grown up in CA, I, of course, immediately noticed the differences in many attractions. Small World at DL has a giant clock as a facade that chimes avery 15 minutes as the dolls circle the front. This was probably not done at WDW to save some money AND because of weather considerations, it would be a great lightning target. Small World also has an updated more "surround sound" soundtrack at DL. POC, much of that attraction at DL is built below ground level, that is simply not possible in Florida because of the high water table. AT DL POC also has a very nice full service restaurant built into the attraction, this was done not only for effect, built because there was a definate lack of table service restaurant in the park at the time of its design. Peter Pan, I actually like the one at WDW better. Many of the attractions at DL have open air queues, allowing a more open and spacious feeling, even in crowded conditions, again...just not possible in the Florida weather.
Now COP at WDW (which I remember from DL) was a better attraction at DL - but far surpasses what is in that building today. America Sings replaced COP at DL, those characters were moved into Splash Mtn, the revolving theater is now a very poor imitation of Innoventions, and is no longer a theater, but a rotating facade
The Mision to Mars (Alien Encounter, Stitches Adventure) building stands empty at DL. TTA (Peoplemover) is gone at DL, and AFAIK, the Circlevision Theater (America the Beatiful) is also still empty.
Space Mountain at DL has a better two abreast seating system, and Splash Mountain at DL has the "Straddle" Logs - so that is better at WDW.
The train around the park goes through a lovely Grand Canyon diorama at DL and that is followed by "Primevil World -Realm of the Dinosaurs" - most of those dinosaurs are in Ellen's Energy Adventure - except for the triceritops and their hatchlings.