I agree...generally speaking a degree will prepare you to someday be a chef, as in provide you with with training in management, menu development, business, communications, ordering/purchasing, inventory management, front of the house operations, and the list goes on.
A certificate will provide you with a solid foundation in cooking techniques, and prepare you to, as it was stated, work the line at a restaurant.
It really depends on what you want out of a culinary program. And I want to clarify that I am saying in no way that a "only" getting a certificate will not prepare you to be a chef. MANY MANY successful chefs did not attend school at all. And geting a degree is no guarantee that you will become a chef. Much of it is subjective.
Just out of curiosity, where are you looking?
Hope this helped.