It's worth going for Cooper alone. Zombie has gotten all this praise for his show on this tour but I honestly didn't see it when I saw the Gruesome Twosome in May. Zombie's show was alright but it wasn't anything special and nowhere near as great as a lot of people are building it up to be on this board.
When I saw Zombie tour with Ozzy in 2001 his show blew Ozzy's away and was a hundred times better than what he did when he tried to follow Alice Cooper this year.
Maybe the venue I saw the show in didn't allow Zombie to set up and do his full show? Either way it was an average performance and Zombie and his band looked like they'd rather be anywhere else than performing that night. There was zero heart or feeling in the performance.
Cooper on the other hand you always get the impression he loves what he's doing and he's playing specifically for you alone. Most important though is that Cooper gives a shit unlike Zombie.