XPS 13" has convertible model. Nowadays Precision laptops come with the same chassis as XPS, nothing premium there as XPS is the regular multimedia laptop. I'd recommend before getting Dell's laptop to first go through the owners comments at the Amazom/reddit/etc, I saw many complaints about quality control and the coil whine problem, so for me Dell is not an option.
A 15" tablet? The 3520 and 7520 have optional touch displays.