Neither.
Well, both to an extent, but green tea, at heart, is something more.
People have been drinking tea for millennia. Not for the anti-oxidants, and not for fashion. The culture of green tea holds a prominence in the Far East, especially China and Japan. The Chinese produce a variety of notable and distinguished greens, from Lungjing to Gunpowder to Bi Lou Chun, and Japan has an extremely complex ceremony surrounding the serving of matcha, powdered green tea, which people train for years to master. The appreciation of tea, especially green tea, has significant branches as close to "home" as Korea, and as far as Morocco.
Just because the West is greatly prone to black tea (notably a culture rooted in ancient trading routes) and is finally coming around to Green tea, is doesn't mean it's just a fashionable or health-related thing. Yes, green tea is good for your health, but if you're drinking it only for that sake, or just to seem hip, you're missing the real point of drinking it.