The one I had had the 8th gen low voltage CPU... i7 8765U or something like that. As a quad core it wasn't bad, though graphics was of course on board. I wanted something really portable rather than a desktop replacement, as I was travelling a lot. Those dual core Intel CPUs aren't terrible, but two cores just isn't enough in many instances. As for Darktable... I thought Lightroom was slow. Then I tried several other raw converters as I was trying to figure out how they deal with the HUAWEI P30 Pros raw files and its color issues, and foud out how poorly most performed. Oh boy
I think Darktable was amongst them. If only Lightroom Classic wasn't a subscription thing. As for the HUAWEI... I figured out, that the ultrawide and regular lens had vignetting that included color shifts... once that was corrected (CornerFix to the rescue!) everything was fine.
The XPS are fine machines, but for some reason I never really got into them. Maybe I will get the chance to try one.
Btw., when I upgraded my desktop, I used my old laptop SSD (which I slimmed down a lot, but it still wasn't that fast) to boot the old desktop components for some tests. It started incredibly fast, despite being an old Windows 10 installation that was upgraded from Vista to 7 to 10... on an entirely different platform. Uninstalling cruft, when combined with reasonably fast hardware, can do wonders. Meanwhile, the Windows installation that was slow on the old hardware, on the same relatively slow SSD, booted much faster on the Ryzen hardware. Switching that 500 MB/s SSD to one that does 3500 MB/s made quite a difference too.
tldr: There are many possible bottlenecks, we would need to know what computer it was to be able to figure out where it makes most sense to upgrade. The biggest changes can usually be seen by switching to an SSD though.