What about the Construction at WDW? Just another thought for your criteria. We had the exact same debate for our March trip. We usually do DL, but have done WDW a couple times. We chose WDW for ours this year, but it was tough. Our top reasons for choosing WDW this time is because of weather mainly. I want to be warm, and March in CA isn't really warm by my standards. Also, as this is a Spring Break trip and we have an entire week, this will give us plenty of time at WDW. At DL, we usually only do 4 days, as it's plenty, so saving DL for when we don't have as much time. Also, as this is my DH's 40th Birthday trip, he wanted to stay onsite. We could of course at DLR, but it's so much more expensive to do so, and not needed there. We stay across the street and walk over. Also, we let the kids help choose, and they wanted to see the new Fantasy Land area now that it's finished. Also, we wanted to take a day to go to Universal to see the Harry Potter stuff.
With that said, I didn't even consider the construction. And am a little bit bummed about that part for WDW, especially at MK. Once we are in the parks I much prefer to be at DLR. My kids don't realize there are 2 parks, they call DCA 'the other side of
Disneyland'. I love that no matter where we are each day, if the kids say I really want to go back and ride 'so and so', we can do it! I don't have to say, 'sorry, we aren't in the right park for that'. I love the quaint feel of DL, and I love the summer/fall weather there, it's not so hot as WDW.
So as you can see we too have reasons for both! The other travel considerations, we are in Texas, and the same length of flights, and generally same cost to fly into each. Hotel, we can save money in CA by staying a good neighbor hotel, but honestly, if you get a deal at even a Mod resort, the nightly rate isn't far off, but of course we stay longer in WDW, so that does add on.
I get your dilemma, hope this helps, and either way we know we will love it either way!