I use the XPS 15 in an office with only mac users and this machine is just more powerful since Apple wont update the Macbook Pro line with developers in mind. I hated working on an under performing laptop when I was using the macs.
And my Mac runs for weeks, sometimes > 2 months, without a reboot. I've had to reboot the XPS on average twice a week (due to crashes, or updates, or really weird performance drops).