Looking at your review of the XPS15 specifically regarding Battery Runtime, I find your statement in this review:
"The Dell XPS can keep up with this performance and even beats the MacBook in two of three tests."
To be confusing. According to your review of the Dell:
http://www.notebookcheck.net/Review-Dell-XPS-15-9530-Late-2013-Notebook.107485.0.html
- Idle (without WLAN, min brightness):
14h 10min (rMBP: 14h 13min)
- WiFi Surfing
8h 50min (rMBP: 9h 11min)
- Load (maximum brightness)
2h 10min (rMBP: 3h 01min)
If I'm reading the two test results correctly, the 15" rMBP beats the XPS15 in all the battery test.
I also think it would be probably be more interesting had you tested and reviewed the base (Iris Pro only) version. That's when the actual usage of Crystalwell makes more sense. Yes, there's performance penalties but the gain in battery runtime makes it an interesting choice.