The discussion with comments from the pros in this other thread might also be interesting.
For me, the main benefit of having a laptop is to be able to carry it around easily and use it anywhere (small and light, touch screen, long battery life) and yet get decent performance (multiple cores, large RAM and SSD disk).
I have no connection to Dell, but I’m very happy with my home setup: XPS13 + large external monitor + thunderbolt hub. If one day I’ll be able to do some serious computing, then I might consider buying an eGPU or a standalone desktop workstation.