Your headline; "Best dirigible Passenger Airship" is redundant. The simple fact that you state it is both a dirigible and an airship is overkill. By nature, an airship is powered and steerable, the same limiting terms apply to dirigible, "a lighter-than-air, powered, steerable aircraft." You might have written, "Best Passenger Airship," "Best Passenger Dirigible," of "Best Passenger Zeppelin." "Zeppelin" is capitalized since it is a proper noun referring to the inventor, Count Zeppelin, the name of the company named after Count Zeppelin and the builder of the EUREKA, and when used to describe a specific type of airship (rigid.)