If you only have one day at Disneyland Resort and do not expect to return for a very long time, or ever :(, go to Disneyland.
The Disney experience is not about rides. If rides are what you want, Knott's Berry Farm is a better choice. Disneyland itself is the destination and experience.
Disney Classics: Small World, Pirates of the Caribbean, The Haunted Mansion, The Jungle Cruise
Thrills: Indiana Jones, Space Mountain, Splash Mountain.
To Enjoy: The Disneyland Railroad, Mark Twain Riverboat, Fantasmic.
Definitely use FastPass and MaxPass. It's worth it for a one day trip. The one 'adult' consideration between the parks is that alcohol is only served at DCA and you are presumably not a member of Club 33.
Also, very important, there are 6 Disney parks in the United States. ;)
Source: Experience, I've been to every Disney park worldwide, multiple times.