They've already done battle over who looks better in a tiara.
But now Christina Aguilera and Fergie are really getting down and dirty. The sexy singers recently rocked the same dress for different occasions, forcing The Hollywood Gossip to ask readers who looks the best in it.
We know who Josh Duhamel would pick, but he doesn't get a vote. Neither does Xtina's husband, Jordan Bratman. It's up to you, the unbiased fan, to show Fergie some love - or let Aguilera know just how awesome you think she is.
As far as our Photo Finish comparisons go, this is a tough one. No doubt. Past competitions, such as whether Matthew McConaughey topless looks better than a half-nude Owen Wilson, were no-brainers compared to this fasion face-off.
So take your time and make a decision. It may be the most important vote you cast until the 2008 Presidential Election.