I eventually decided on openSUSE Tumbleweed for a few reasons: rolling release, because I like to stay up-to-date; non-derivative, not a fork or dependent on other underlying distros; European, for (perceived) privacy reasons; a relatively well known and large distro with a decent community, for troubleshooting reasons; backed by a company, though that has both its ups and downs; lastly, support for KDE Plasma.
I actually had trouble finding a distro that suited all my criteria at the time, but openSUSE is good enough for now and I am pretty much satisfied.
Mandriva is gone, but there's a couple of projects carrying its legacy. OpenMandriva is one of them, obviously. Mandrake was my first distro too, so I have a soft spot for it.
From my perspective, OpenMandriva's biggest strengths are that it's independent, non-derivative, community driven, and based in Europe. Unfortunately it's also small, but the people behind it seemingly do a lot with very little, so the community is passionate about the project.
Personally I'm just happy that there are smaller, non-corporate distros still out there providing alternatives. And OMLx seems like a pretty solid distro at that.
For their selling pitch, you can check their FAQ.