Girls Aloud - both looks-wise and as a band. They had some really catchy tunes, and they're an eye candy. I'm not exactly a fan of them or modern pop music in general, but I really liked the 80's vibe in their songs and their energy.
Sugababes are one of the most talentless bands I've ever had a misfortune to hear. Crap vocals, samey music, that black chick can't sing for the life of her.