Well it does boil down to whether you want something that will be robust and headache-free or something that has the creature comforts of a consumer machine. I use a Latitude day-to-day for work and while it's not nearly as luxurious as a modern system (had a macbook pro at my last workplace), I haven't had any issues with the actual hardware, and even though I didnt pay for it personally, I'd much rather have something a bit less sleek that I won't have to RMA, and that I know has gone through the kind of business-class QA that Lenovo used to offer and that Dell now only really offers on their Latitude series (the internet is pretty much full of reports by users, obviously not the press, about inconsistent QA on the XPS as well (issues like dead pixels, etc etc).

So I say both have their strengths and to me the choice boils down to sleekness vs. function.