The Dell XPS 13 Ultrabook has a native FHD resolution. Comparing like for like, the performance drop-off is much greater in F1 2017 run at ultra settings. The desktop machine is 60 per cent faster at 1080p, though in a more practical sense, the Ultrabook performance is more than adequate.
Here is the same comparison but at 4K. Not as fast as a desktop, sure, and the drop-off is limited to around 20 per cent. You might imagine that playing over Thunderbolt 3 will introduce latencies that aren't obvious in FPS charts. That's not the case, and whilst not as elegant as running on a standard PC, F1 is smooth and fast at 4K.
A similar, but less pronounced, story in Middle-earth: Shadow of War. You are never going to match a desktop system at an FHD resolution, and you should expect a 20 per cent framerate deficit when running 4K.
Hmm. Total War: Warhammer II shows a different side to external GPU boxes. The FHD performance drop-off is far more considerable, almost halving framerate, and even 4K takes a big enough bashing to stop the game being reasonably smooth.
On the other hand, you are never, ever going to get close to this performance on any Ultrabook, so whilst not perfect by a long shot, an external GPU enclosure makes sense for the well-heeled gamer without a desktop gaming system.
Looking at other important metrics, the XG Station Pro consumed 206 watts when full-out gaming, and the reference card hit a peak 86°C and 1,720MHz boost speed.