I loved both, but I think I liked Hero more, just because I was getting in to the story. They're both really really really different movies. Depends what kind of mood you're in to see whichever.
Hero, if you're pumped. Garden State if you want to see a really cute, sweet movie, but it's still really clever. Loved both.
Edit: And in Hero's defence, it's not average IMO. How many times have you seen a martial arts flick with a decent story? I mean, it was better than the crud we get in America, remember all those Jackie Chan movies when they came to America? Jesus.
And on top of a *decent* story (and an all right attempt to tell it, though it got confusing for a little bit but cleared up later on), the visuals are just really nice to look at. Why drill it when it's still interesting to simply look at, let alone follow the story and so on. Fighting was great too, and there isn't THAT much talking. There's talking, and then a fight, ad nauseum. The whole movie is just a series of fights!