We also live in NZ (can't wait for the new Houston direct flight!), we basically alternate both and love them both for different reasons.
There is a thread over on the
Disneyland boards called something like Disneyland for WDW vets. It is excellent.
Some quick points:
-I would definitely recommend a hopper ticket as the two parks are so close together that we treat them as one park.
-The ride concentration is excellent, there is as many between the 2 parks as between WDWs 4
-If you are going after May 22nd there will be a new parade and fireworks show to celebrate the 60th anniversary, I think there will be a new WOC as well
-The planning will probably drive you a little nuts (or maybe you will love the lack of it) the hours are not released until about 60 days out, dining cannot be booked until then either0dining doesn't book out like at WDW so you still have a good chance booking a couple of weeks out
-Be prepared Sleeping Beauty's castle is underwhelming compared to Cinderellas but there is a really cute walk through
-check historical hours, depending on the time of year you plan to travel the have a real off season where the parade and fireworks are weekends only and the parks shut pretty early plus loads of refurbs.
-As of now still FP-
-It is nowhere near as important to stay onsite, check the good neighbour hotels, some of them are closer to the parks as the onsite ones.
-Not getting into which rides are better, people have different opinions on this but Carsland is unlike anything WDW has and if you have are going between Sept and Jan the Holidays Haunted Mansion is the best!
I think it is worth the trip, we normally spend 5-10 days at DL (NZer's can buy a 10 day ticket-you will be capped at 5) then we check out other LA's offerings and drive to San Diego for SeaWorld/the Zoo.
I agree with McNs that when we are in Orlando we tend to do theme parks only(we do US, SW and drive to Tampa for BG) plus some shopping but we have done the Space Centre and things in the past, it is just that the LA area has more other things depending on your trip length