I'd say that it's best to plan your touring around ADR's, but only if you CAN'T get online and see the EMH for the date you will be there. For instance, I just booked for June. I think I can call and get my CRT and CM ADR (or at least soon). I will plan those out and then plan other days at the parks. I didn't look to see if the EMH calendar was out for June yet, but I also can't make a normal ADR yet, either (the system is only working until March right now).
I think going to a non-EMH morning park would help get a lunch or breakfast ADR and going to a non-evening EMH park would get you a better chance of a dinner ADR in a restaurant. Does that make sense? Think of it this way- if everyone from the resorts will already know they can get to a park early or late, don't you think those people would plan accordingly? That's been my strategy and it's worked great so far, with the exception of EMH mornings at Epcot, where I got the pickings of any restaurant I wanted for an early lunch...But at MK or AK, getting the ADR you just have to have and getting there on EMH are two conflicting strategies because of the small selection of restaurants.