I'm relatively sure that xihu is considered the best. It's all down to
leaf quality and the other typical measures to tell a better tea from a
worse tea. With longjing it's 1 stem, 1 leaf and the smaller the
leaves the better. The color is also important...I'm sure jing can
elaborate on it more.

Jing: you run a teashop in GZ? I'm going to gz this weekend, and I
could stop by.