I like Linux Mint 17.3 Cinnamon so much that I have replaced Linux Mint 17.2 XFCE with it. Cinnamon just seems a bit more up-to-date and not a throwback to an earlier era. It is prettier, which inspires confidence and promotes harmony. XFCE just seems crude, somehow, in its icons and layout. I also like the ease with which the look and feel of Cinnamon can be customized.
It is a pity that Linux Mint is about the only Linux distribution I have any use for, besides occasional forays into Xubuntu. The other distros just seem, well, primitive or lacking in some way to someone coming from the Ubuntu family of distributions. I wonder why the other distros don't improve their user interface in order to compete with Ubuntu. Perhaps they are bound by tradition and only serve a small group of veteran users or specialized applications. Perhaps Open Suse is the sandbox for Suse Enterprise, while Fedora is the sandbox for Red Hat. PCLinuxOS is missing a lot of software, and one has to make peace with giving up applications forever in order to use it. Debian seems geared for servers. Mageia may be promising but seems not to offer anything special over Ubuntu. I don't know that there is a really strong competitor to Ubuntu and its derivatives at this time. The best that can said about the other distributions is that they are almost as good or comparable with Ubuntu or Linux Mint in one way or another.
ArchLinux and moreover, the M- distro (I forget the name, but apparently it has its own separate repo's) seem tempting from time to time, but I really don't want to spend hours tweaking my OS to get things working, and I do not like the idea of a rolling distribution either, in which things can break. I like the idea of updates that trickle in slowly, after being vetted by the veterans, not updates that can break my printer or cause my computer not to boot at all. I also want access to the Debian world, which Ubuntu provides. It is important for me to have easy access to all available software applications. A distribution that cannot offer that is not one I would consider. I am afraid Open Suse and PCLinuxOS were missing some programs in their repositories during the times I evaluated them.
At this time, I don't know of any compelling reason not to use Ubuntu/Linux Mint. However, I certainly hope the MIR/Wayland brouhaha does not get out of hand, and that Ubuntu is wise enough to offer easy access to Wayland, so that everybody can just get along. What we do not need is a scenario where stuff breaks in Ubuntu because it was made for Wayland.