At this point, you may be wondering which Mandriva-based distribution I would recommend. This may come as a surprise to you, but I think that both Mageia and PCLinuxOS offer everything a newer user could possibly need. Both distributions offer a strong, Mandriva-flavored control center. Both have great hardware support and make connecting to your network a snap.
Where the two distributions differ, however, is in the front-end to the software management and how users keeps their systems up to date. PCLinuxOS offers their users a rolling release cycle, so that, in theory, you only need install the distro one time. Mageia on the other hand, offers its distribution as individual releases. Both are well maintained and up to date, but some may argue that PCLinuxOS is "easier" because you don't need to worry about upgrading the distro.
Now this isn't to say that PCLinuxOS doesn't offer release versions. However the way users of this distribution enjoy these new releases is by simply keeping their system up to date—that's all one needs to do. Mageia, on the other hand, changes from release to release, so you would upgrade using either a provided GUI or a set of commands. This reminds me a bit of how Ubuntu handles distribution upgrades. And like Ubuntu, it's recommended you ALWAYS backup your home directory before upgrading.
This difference in kernels means that if you own brand new hardware, then Mageia may be a better choice for you since it's more likely to support your PC. PCLinuxOS, offers an older kernel that is going to be safe and stable for slightly older hardware.
So what about OpenMandriva then? Is this distribution even a factor at this point? To be brutally honest, it's not really worth bothering with. Perhaps in a year or two, it will be worth looking into, but as it stands today, it's simply an alpha quality distribution not yet ready for the masses. Besides, I fail to see what it's going to offer that Mageia hasn't already addressed.
In this article I shared some history about Mandriva and the forked distributions inspired by it. After understanding a bit more about these Mandriva forks, I then explained the differences between these distros by comparing the benefits of PCLinuxOS's rolling release model and how Mageia has the mainline Mandriva-style upgrade approach.
The big takeaway is that the two distributions worth checking out are quite different despite both being descended from Mandriva. I remain convinced that for those seeking stability, PCLinuxOS is where it's at and those who want a more cutting edge experience will be happy with Mageia.
I remain unclear as to where OpenMandriva will fit into all of this. After all, it's brand new, and unless it offers something drastically different from Mageia, I honestly don't see why anyone is going to bother with it.