Dell XPS12 vs Yoga 2 Pro

Hello, I'm a student who wants to buy an ultrabook. I will be using it for writing and entertainment (browsing the internet, watching movies, no games). Strong battery, good keyboard and trackpad, lightness, portability and nice screen are the most important for me. Good build quality and design wouldn't hurt as well. I like the idea of a tablet/laptop hybrid, since my Nexus 7 died recently, but something of a form of Acer S7/Samsung Ativ Book 9 Plus wouldn't be bad I think. Right now, Dell XPS12 (with Haswell) and Yoga 2 Pro are main favourities for me. However I'm not so sure about the screen size and trackpad in the Dell and battery in Yoga 2 Pro. Which one of these should I choose?