I decided between the MBP and the XPS 15. I went with the latter, and haven't regret it. The design is different, with the MBP probably having a more exclusive design, but I think the build quality is the same between the XPS and MBP. I have had zero issues which the XPS, which is something a fair deal of MBP 2016 cannot claim, unfortunately.
The fans of my XPS do spin up when doing graphics-intensive stuff, but as of right now where I'm just surfing, working in PowerPoint and Outlook, it is dead silent. In practice, I get 6-7 hours of use per charge, whereas other computers (but maybe not the MBP?) get 8-9 hours. Not a big deal to me, but of course this is the downsize to the 4K IPS-screen.
For me, the thin bezel and the ability to change HD, RAM and battery are positives. Each to his own, of course.
If you're a photographer, the built-in SD card reader would be considered a clear advantage for the XPS. For high-resolution pictures in RAW format, which most photographers I know use, wireless transfer is simply way too slow. Having to carry around (and connect) a TB3 card reader to import photos is definitely possible, but I fail to understand why it should be necessary. I have never understood why Apple chose to drop the card reader in their PRO laptop. But again, maybe it's just me.
It sounds like the XPS checked off more of your boxes than it did for me. I hope you love it! There are a lot of people who do, I just wasn't super happy with it. My father took mine off my hands, and he gets along with it just fine. Way more functional than the old Latitudes he is used to.