Final answer:
The distinguishing feature between the Diamond DA-20 Katana and the Diamond DA-40 Diamond Star is the landing gear type, with both aircraft featuring tricycle gear, but the DA-40 being the more advanced model.
Step-by-step explanation:
The feature that distinguishes the Diamond DA-20 Katana from the Diamond DA-40 Diamond Star is the landing gear type. The DA-20 Katana typically has a tricycle landing gear setup which is common among light training aircraft. In contrast, the DA-40 Diamond Star also features tricycle gear but is more advanced with aspects such as a constant speed propeller, a larger cabin, and may come equipped with advanced avionics depending on the specific model.