Britney Spears & Jennifer Lopez
Both debuted in 1999.
Both are known for being great dancers but horrible singers.
Both were reality show judges.
Both slay in Vegas know.
Although the only difference is JLo faded kind of quickly and Britney has way more longevity over her.
Britney is way more successful.
Way more.
Lady Gaga and Cyndi Lauper. First era is a huge success with several smash hits. Second era also quite successful riding off the coattails of the previous era. Third era still gets a top ten hit but album sales are tragic.