Compared to the CP/M box it replaced, the IBM PC was a speed demon.
Z-80 software would presumably be harder to translate, although the x86 has additional registers and instructions you could use.
 the rumored easter egg of a Gary Kildall or DRI copyright message hidden in MS-DOS or QDOS was never found, sadly
In some ways that is the moral equivalent -- the function was copied without fully understanding the why of the function.
I'd not read that Tim Paterson story before. I have read the reverse: he built the filesystem for the Japanese 8-bit MSX computers under a Z80 emulator on MS-DOS, using IBM's BIOS for actual disk I/O. https://www.msx.org/wiki/The_History_of_MSX-DOS
> Los Angeles is the 8080, San Francisco is the Z80, Sydney is the 8086, Catholicism is CP/M-86, and Protestantism is MS-DOS.
is officially my new favorite out-of-context quote about early microprocessors and operating systems.
> As many of us home computer users begin transitioning to the IBM PC with its 16-bit Intel 8088 CPU and new IBM PC DOS operating system, we need not bid farewell to our CP/M programs.
Wordstar 3.3 for MSDOS was an exact clone of the CP/M WordStar 3.0 that was released a year or two earlier. Even some of the data sections were in the same place, such that you could copy parts of the configuration data from the CP/M version across to the MSDOS version.