I won't get into Resort vs. Resort, but having lived in both areas, I feel pretty comfortable discussing the Magic Kingdom vs. Disneyland. They are both, obviously, great ... but I prefer Disneyland. Here's why:
Adventureland:
* Original Tiki Room show
* Indiana Jones is the best ride in either park and fits in thematically perfectly.
* The Flying Carpets take away from the immersive experience of MK's Adventureland, in my opinion. It ruins the atmosphere.
New Orleans Square:
* Pirates is far better.
* The Blue Bayou is the best restaurant experience in either park.
Frontierland:
* Fantasmic in DL is a better experience than DHS, imo.
Fantasyland:
* The "castle stone" facades are much, much better.
* No roof on the tea cups greatly improves the experience, particularly at night.
* Mr. Toad still exists.
* Matterhorn - nothing comparable in MK.
* The subs still exist, even though they've been Nemo-ized.
* IASW facade is beautiful and iconic. The outdoor load area adds to the experience.
Tomorrowland:
* The Space Mountain ride is better. The ride vehicles are much more comfortable. However, it's 2nd floor outdoor queue detracts from the exterior appearance of the building, imo.
* The "live music venue" aspect of the Tomorrowland Terrace (particularly when you get a fun cover band) - nothing comparable in MK.
Main Street USA:
* The stores have not completely been "Emporium-ized" yet. It's not one big store the entire length of Main Street. Adds greatly to the atmosphere.
* The Grand Canyon/Primeval World Diorama has no comparison in MK.
* I can't speak for the new fireworks, but Remember Dreams Come True was the best fireworks show either park has ever seen. I'm actually shocked they changed it already.
* During the day (particularly in the summer), there are less people and far, far less stollers and motorized carts.
Admittedly, the Magic Kingdom is better in many aspects:
* Most importantly, it's just so much bigger. On a crowded day, Disneyland can make you clostrophobic because you have people packed right on top of you.
* The Pirates queue is far better.
* The Haunted Mansion seems grander because of it's location inside the park.
* Country Bears
* The Hall of Presidents is much better than Moments with Mr. Lincoln.
* I'd call Liberty Square vs. New Orleans Square a tie on themeing.
* The castle is much larger and nicer.
* Tomorrowland actually looks like it has a cohesive theme.
* TTA is up and running
* The Rocket Jets look impressive because of where it's located.
* You don't have people camping out for Fantasmic two hours before it starts and causing massive traffic congestion for the whole west side of the park.
* Similarly, you won't get completely trampled at the conclusion of the fireworks.
* While it doesn't even exist in MK, Star Tours in DHS has much nicer exterior themeing than the one in Disneyland.
As has been pointed out, Resort vs. Resort, there's no comparison. DCA isn't even half as nice as DHS. And there's nothing to compare with Epcot or AK. No waterparks, only one premium themed resort hotel, no golf courses. The monorail is mostly a novelty, instead of intrical to the resort transportation. And most importantly, you can't just get on property and forget about the outside world for a week - you're always going to know you're in the middle of the city (there's not enough separation from the outside, the city is right on top of you).