Are you only limiting yourself to these 2 headphones because you're more worried about "looks" above sound quality?
The Beats aren't good at all, whether you get the smaller or bigger version. The bass is deep, but the lows and mids are muffled. It's like listening to music underwater. I don't know the US price of the Beats by Dre, but in my opinion, they shouldn't cost more than $100. If you pay any more than that, you're paying way too much for what you get, even if you add a "I want to be trendy" tax to the price.
I listen to rap, and between the two options you have, I'd get the B&W P5.
If you want something that looks awesome, and has a similar sound signature as the Beats (lots of bass, bad lows and mids), you may want to consider the Klipsch headphones.
Oh, I have the Phiaton MS400s. They look AND sound good, and are cheaper .
The B&W P5 doesn't sound better or worse than my Phiaton, but definitely different.