If it's only for the kids, they will love Disneyland more as there are more cartoon characters and it's more colorful there. My 5 yrs old daughter said if there's only one park to choose, she will opt for Disneyland (after she went both parks).
But as for adults, I like DisneySea more. It's less crowded there and the shows (espcially the one about rainforest) are awesome.
If u have never go to the both parks before, I suggest u go to Land first.
My 6 yrs old son went to Land last year, so we went to Sea in the middle of this month. My son enjoy it very much, he can play the games again and again.