ThinkPad X1 Carbon or MacBook Air 13' ?

So I'm in the market for a new laptop next month and I've come to a crossroads. Whatever machine I buy will have to run Windows as I rely on Microsoft services a lot and just generally know and enjoy Windows. However, I can't decide between 2 machines, the ThinkPad X1 Carbon and MacBook Air 13'.

Now I know everyone will say the MacBook isn't a Windows machine, but if I bought one, I fully intend installing Windows through Boot Camp.

So any owners of these machines, what do you think ? Why do you love yours so much ?

And anyone else, why do you think one is better than the other ?