I still can't stand 16:9 screens (unless bigger than 17 inches) that Dell uses, 4K or not. The 16:10 on the rMBP is why I keep going back to mac. However, if Apple releases another rMBP 'update' this year with a 28nm dGPU, I'll probably looking elsewhere. My 2012 rMBP 15 is getting pretty outdated this days as it's weak CPU/GPU/8gb/512gb SSD is constraining me. The XPS 15 has 2x M2 slots so you can go 512gbX2 and of course there will be bigger SSD's soon that you can drop in. Heck, even the ram is upgradable!