Thread starter stated a 5K budget, so an MBP is out of the question.

I'd go with the XPS. The MacBook is underpowered in comparison to the XPS, and it's so rabidly popular that there's little appeal in owning one unless you're committed to switching to OS X. Upgrade the XPS M1330 a bit with the 8400GS, LED-backlit display, and you'll end up with a light and powerful machine.