If you're willing to spend your money on a great show: see Britney. I can't believe I am actually saying this, but I want to go to that tour too because of the fact: the stage is nice, Britney is a legend, and Nicki Minaj is on it (+Adrien Gallo ).
If I was you I'd see Katy. Her voice sounds amazing on tour and she puts on a great show. It was on par with the monsterball. There both good though. I'm seeing Britney in November as well as Katy again in October
I'd go for Britney if I were you. You don't know when and if she'll come back around with a tour, maybe she won't and if that's the case you'll regret choosing Katy over Britney. Katy is still on her first worldwide tour and it's pretty much a given that she'll return with a second tour. Unless you have already seen Britney before of course, then I'd go for Katy.
).