The CY in Marina Del Rey is a great location. You won't need a car, dinner, movies, walking, the marina all close.
MB Marriott is old and needs some updating and has a few things close by, Fry's, movies, dinner. Great refinery views too.
Stay at the CY in the marina. You'll be glad you did. One downside to the Marina Del Rey location, noise. Close to PCH and 90 freeways, no freeway noise just a lot of cars.