It's WDW every time for us, even though we've had to swap the 8hr flights for 28hr ones after moving here. We've done DL twice (1987 and 2013), but even on that most recent trip it was combined with WDW. We used the DL trip as a layover opportunity. Whilst it was great to do some of the rides we've never done before, we still missed the magnitude of WDW. You also have the added bonus of the two main additional parks, the two water parks, plus all the other parks and attractions that Orlando has to offer. There is so much to do at WDW, that even now, on the umpteenth visit, we are still finding new things to do. The first few years we went, we planned with military precision, but it doesn't work. Something always comes up and things go wrong. So, these days, we plan our restaurants and tours/activities ahead of time, but the park visiting, we just 'go with the flow'. We have thrown in a cruise before, and will be doing so on our next trip this year. So many cruises are available out of Sydney, but having done a Disney one, I am spoiled, and would probably only do a non-Disney one if rates were exceptional. The cruise is great for having a few days and nights away from the hustle and bustle of the parks, and gives you some great downtime. It's good to throw into the middle of the holiday too, so that you can ensure you are in mainland USA/Orlando before the cruise date, and so you have time to re-group after your return before having to head home.
Flight wise, the first year coming from Oz we laid over in LA on the way out, and straight back on the return. However, after that first time, we've just done the 3-4hr layover and got on with it! We've looked at flying Qantas/American (via Fort Worth), but they are usually $1000+ per person more expensive than Delta/Virgin Australia. We go Delta via LA. Normally, we are not able to lock in dates until close to time, so flights about $2500-3000 per person, round trip. This year, we were able to plan a bit more in advance, as I will have finished uni again, and we got them much cheaper. Delta have been amazing. We got diverted to Hawaii one year because a staff member had a heart attack, and received credits to our accounts. Then last year, we were delayed out of Orlando because of severe thunderstorms, and had 30-minutes once we landed in LA to make the connection. There were about 10 of us, and the on-board crew made sure we put our call bells on so the entire plane could see who had to get off first. Then, when we landed, everyone was asked to remain in their seats until those of use for Sydney had got off. A few people got up and in the way, but on the whole everyone was helpful - the staff did a great job in making everyone feel empathetic saying if we miss the connection we'd be camping in the airport for 24-hrs until tomorrow's flight!
Ticketing is the worst part, as from here, we always go for much longer than the average American. It's part of the reason why MYW tickets only go 10-days. Anything past that, and you might as well get the annual pass. The Gold annual pass is now available to DVC members too, which is our plan this time. However, we try to be clever with bookings were we can, and go just within a year of our previous visit. i.e 15-31 August one year, 1-14 August the next year, so that we get two years' worth of vacations out of a one-year annual pass!