Ask HN: What should I buy? Macbook Air or Dell XPS 13?

I'm looking for a Linux (well, Unix based) laptop for programming. XPS 13 is too tempting. How does it compare with Macbook Air in terms of performance (mainly SSD)? Also, would you recommend getting XPS 13 and installing Linux? or get the XPS 13 Developer Edition?

I have not used Mac yet and am not a fanboy of Apple (yet!). Anyone who has used both?

Thanks!