I’m not a fan of either, but it always seemed to me that Cristina was trying to catch up with Britney. The first singles, the evolving sex themes, the orgy videos… I think Aguilera even got pregnant right after Britney.
She was kind of ripping off Britney. When Spears finally broke down and stopped producing, Cristina even had her best work. It was similar to the Stones and Beatles situation, but on a really lower level of musicianship. Cristina was the most talented singer, and sold herself as an edgier Britney, but was not really in Britney’s league in terms of generating interest.