Results: SiSoftware Sandra
This top-end XPS One's Core i7-3770S has a huge advantage in Sandra Arithmetic, though even the older notebook's Core i7-3610QM beats the Core i5-equipped desktops.
The XPS One 17" falls behind a bit in Sandra's Cryptography, which we know to be indicative of a memory bandwidth disadvantage since AES-NI feeds the processor instructions as fast as they can be loaded from RAM.
And as suspected, our bandwidth numbers are slightly lower than the platforms we're using to compare. That raises the question why so many SO-DIMM-equipped machines employ DDR3-1600 CAS 11, when DDR3-1600 CAS 9 is really quite economical now?