Touring doesn't have that much to do with the actual music industry because you can't steal concert tickets like you can music. Obviously Britney has had a larger amount of successful tours, but Gaga outgrossed them all with her first major tour. I don't know!
7 tours in, and Britney is still dominating the world with her concerts. Gaga is doing amazing so far, but no one can guarantee that she will still be pulling huge numbers like Britney in a decade. So far, Britney is the biggest tour act. The DWAD DVD remains one of Pop's most Iconic DVDs of all time.
If you add inflation to Britney's earlier tours, everyone trying to mention gross will STFU.
Uh, no... Not really. Even with inflation her highest gross is still the Circus tour which bumps up to about 142 million. Her biggest tour before that only grossed 43.7 million, and that does not jump all the way past 200 million.