Hm, well to be fair I've only ever been to Magic Kingdom in Florida, but judging from looking at the attractions, and the atmosphere, I'd say it's the better one of the two.
The castle is the first thing I notice about both the parks, and there's no doubt in my mind that even with the recent paint job, the one at Magic Kingdom is better. That doesn't make it a better park by any means, but it sure does help with the atmosphere, and it's the first thing I think of when I think of both parks, so it's only fair I compare the two.
As for attractions, it seems as though Walt Disney has more, looking at the websites as well as the list UC provided. All the attractions are themed well at either park, so it's hard to choose one over the other.
I'm also inclined to say that the atmosphere on Main Street is better in Florida, but I don't think I've found enough pictures of Disneyland's Main Street to make a better judgement.
But, overall I think Magic Kingdom would win, but my opinion isn't entirely fair due to the fact I havn't been to both, and so on.