Linux Experts

For the Linux users out there, I need some opinions/answers. I've got an older Windows machine that I am thinking of reviving with a Linux OS. I am also considering a Linux dual boot system, with Linux on a thumb drive while the original Windows OS on the HD. That would give me access to all the stories, photos, and what-not.

My question is which would be a better choice: Ubuntu or Mint? Either one can be installed on the HD or a thumb drive. I like the thumb drive option for it's portability. Any suggestions or recommendations?