Hurd is based on Mach and available for x86 only. You can run X11 and Debian packages. Drivers for Linux have been ported. Debian/Hurd re-uses some of the Debian community infrastructure for development. Has a goal ("viable for everyday use, and gives users and programs as much control over their computing environment as possible"). The focus yields things at the intersection of research/pragmatic use (e.g., introducing novel features like translators).

Minix is less mature from a community standpoint and its development processes. It's developed and run by about half a dozen contributors (generous estimate). Mostly students. Lacks leadership. It runs on x86 and arm. The microkernel design is its own. It's been possible to run X on past versions, but despite other comments, X11 is not actually usable on the latest release (3.3.0, released 2014 September). No (graphical) web browser has ever been ported. Running primarily parts of the NetBSD userspace. Not so much interest in taking advantage of the modular design to introduce novel features; implicit focus on porting existing BSD packages instead.

Minix 3 doesn't have Debian userspace :)

how far along is Minix 3?