While Coffee Lake-H has been benchmarked and compared with Kaby Lake on this site before, the real-world performance of CPUs more than ever depends on the engineering and implementation of each system. In such a thin-and-light chassis as the XPS 15, thermal constants have traditionally left their mark in performance. The XPS 15 9570 with i7-8750H CPU, however, has performed surprisingly well in our initial tests.
https://www.notebookcheck.net/The-XPS-15-9570-with-i7-8750H-CPU-is-almost-twice-as-fast-as-its-predecessor.308578.0.html