I'd rather not sideline this with a discussion about resolution and brightness, because frankly, it's one of those subjective, "try it yourself and see what works best for you" sort of things. In short, I view high brightness as a drawback, not a feature, and the resolution + font size is more important on OS X, where I have a much harder time getting everything to a reasonable size for me in concert.
I'm willing to bet none of that sounds familiar - as I said, it's one of those things where, if you have to ask, it's not an issue for you. All I can recommend in your case is that, if you're considering an XPS13, take look at one of the XPS13 models and seeing if that display works for you or not.