Better out-of-the-box desktop experience. Last time I tried Debian for desktop, I tried for 4 hours to get my bluetooth headphones to work. In Linux Mint (or Ubuntu) they just worked out-of-the-box.
They work out of the box on Debian now too. Ubuntu used to do all sorts of upstream work to make Debian unstable work better, but nowadays Debian is on par with Ubuntu for post-install usability.
