One of the reasons I still own and ride a classic steel road bike is that it looks beautiful. I wear retro jerseys (amongst others) because they look cool. But I wear a modern Giro helmet because IT WORKS. Apparently there is technically still a debate about this, but having put a dent in a car door with my head and having the helmet crack to be unusable afterwards, I'm willing to believe I made the right choice in wearing it.

(Actually I think the Giro helmets look pretty good anyway, and they're very comfortable.)