We have taken at least two trips on each of the annual passes. Before the dining plan and ticket changes it used to be cost effective to buy an AP if you were planning on visiting the parks for more than 10 days. I can't compare now because I haven't done the math since all the changes. We definitely get our money's worth out of the passes....we are going down for a month in December and hopefully will get in at least one or two trips until next December. I just love the whole WDW experience for our family and also the flexibility the AP's give us. We can go to as many parks for as many days as we want and never feel rushed etc. (I'm sure the magic your way tickets with park hopper give you the same options but we go for too long to make this work for us) I have been to dl and for me I can't compare the two as WDW is in a league of its own as far as I'm concerned. My dd6 enjoys MK as much as EP. In fact she may even choose EP over MK some days. She likes wandering the countries as much as we do!
As far as I'm concerned an AP in WDW is the way to go. But again, we go for way more than 10 days so you'd have to sit down and figure out the cost effectiveness. I think when Disney was offering the free dining that would have been a great perk...but again, not for longer stays.
Just be prepared if you do go to WDW. We ventured down there for our first trip in 2002......this was supposed to be a once in a lifetime trip and we'd try other places every year.

And for some reason it just keeps calling us back. It's the pixie dust they throw in the air....I think we're addicted!