Check out who is rocking killer threads and who needs to put their stylist on (permanent?) timeout this week.

Best: Rihanna

Rihanna has become one of the fashion world's favorite artists with her penchant for leather and bustiers. The singer lived up to our fashion expectations as she rang in the New Year at Jay Z’s 40/40 Club on January 31, in NYC with model Cara Delevingne. The “Pour It Up” singer worked a black bustier and white satin platinum suit as she cooked with her crew and did Cara’s hair before they left for the party.

Rihanna styled the spicy look with a killer pair of hot pink Manolo Blahnik pumps and a matching pout. Equal parts glamorous starlet and sultry hottie, we love Rih-Rih’s first outfit of 2014.

Worst: Katy Perry

Katy Perry has been hitting some extreme highs and lows with her style lately. Perry hit yet another low as she attended the opening of “Britney: Piece of Me” at Planet Hollywood Resort & Casino on December 27, in Las Vegas, Nevada. Perry took to the red carpet alongside Selena Gomez, Adam Lambert and Sia wearing what looked like her pajammas – an iridescent, baggy UNIF tee complete with black varsity print that stated NU FRENZ.

The singer styled the teen schoolgirl look with a fluffy white tulle skirt, black over-the-knee socks and matching boots. Just when you thought the look couldn’t get any more adolescent, Perry flashed her tiny, hot pink metallic backpack.