For me it's definetly Zoo TV. Believe me, I think PopMart was great too, but Zoo TV just had something special about it. The different stage personas of Bono, and the feeling it was more than songs being played. The mocking with the media in such an ironic way is just fantastic. Unfortunately I'm too young to have ever seen either Zoo TV or PopMart
) The songs were great live (even if Bono's voice was not good every night), even the setlist was pretty much the same every night, and I like the Edge's guitar sound 