As a linux laptop, Dell XPS 13 (model 9343) is perfect, running ubuntu 14.04.3 LTS with gnome for 6 months now, extremely happy with it.

Best laptop i ever had, and i am including macbooks & thinkpads in the comparason.

I would recommend going with with windows version, then install ubuntu on it, since it comes in much more configuration options than preinstalled ubuntu version.

Bios trick to create boot entry:

Be careful though, this is the previous model.

The new one, (model #9350), the one with thunderbolt port has some issues depending on the kernel version you have.