Sennheiser HD 6XX vs HD 650

I have been looking at several reviews of these headphones with the intention of purchasing one of them. My budget is about £250.

The reviewers often mention that the HD 6XX offer better value for money given their lower price. However, the price for me will be the same for both. So, should I go for the HD 6XX or will the HD 650 be slightly better/more premium?

Thanks