“I guess one advantage of a navy suit is that the jacket can be worn to create the “blue blazer” look when paired with khakis for a slightly businessy business casual occasion. Again, this is for the East Coast. Here, that would be “dressy.””
In a pinch you could repurpose a navy suit jacket that way, but a blazer actually is different. The archetypal blue blazer worn with khakis has brass buttons and is cut differently. It’s also a slightly lighter navy.