I don't actually like retina displays for tech work. I think it's purely cosmetic, and it generally slows things down. But worse than that are glossy screens. The 1080p x1 screen is perfect for me at 13", no scaling required, it's matte, and it's still in HiDPI territory so plenty of screen real estate. You can also get the 1440p screen if you want more pixels.

Ram-wise, 16Gi is plenty for me. The nvme ssd more than makes up for any issues. I regularly run multiple IntelliJ/Goland windows, docker containers, VMs, etc. without a problem. If I need more, I have a proper desktop. Laptops are meant to be portable.

The carbon is half a pound lighter than the comparable macbook pro, and better in all respects that matter to me - keyboard, weight, battery life, repairability, durability, linux compatibility.

Comparing the X1 carbon or other ultra-portables in the X series with an XPS15 isn't really fair - and the 16GB is a limitation of Intels mobile ('U' series) processors, hence the same issue with Apple.

A fairer comparison to the 15" machine would be either the T580 or P51 series which has a similar choice of up to 32GB RAM and up to even Xeon processors if that's your bag - perhaps not quite as sleek as the Dell, but then it is a Thinkpad.