Which is more easy to use, Ubuntu, or Mandriva?

I think mandriva is the best, and easiest.

I prefer Ubuntu, but I doubt there is any hugely notable differences.

I have used both. I have to say Ubuntu is a lot easier to use and understand for someone who's migrating from Windows. There's a lot of support and documentation, the community is great and the amount of software available is amazing. I think Ubuntu has won the popularity contest. I am currently using Ubuntu and I can't complain. PCLinuxOS is another OS based on Mandriva that is good for beginners.

Ubuntu. No questions. I’ve installed Mandriva for someone who used Ubuntu before,
and they requested that I install Ubuntu instead.