The XPS 12 is not a tablet, its a convertible laptop. I have both a Dell XPS 12 as well as a Lenovo Tablet 2 and use them for completely different things. The Dell XPS 12 is too heavy and does not have the battery life to be a tablet replacement, and the Lenovo Tablet 2 does not have the processor to be a laptop replacement. Together though they work very well.
Comparing the XPS 12's to tablets is an apples to oranges comparison, they just aren't similar. A better comparison is XPS 12 vs. touchscreen ultrabooks.