Obviously Gaga
Britney was always overshadowed by the likes of Eminem, Linkin Park and Backstreet Boys while Gaga was the undisputed top bitch during her peak
Literally the only thing Britney has over Gaga is album sales (Gaga obviously wins when it comes to tours, acclaim, singles success, recurrent airplay) and we all know that the market during Britney's years was 3x as big as during Gaga's peak and that if the market stayed the same, Gaga would've outsold her ass effortlessly
