I was wondering what is the difference between mint linux and ubuntu in regards to something other than the interface. When I look this up on google everything seems to be about Unity vs Cinnamon. What other major differences are there between ubuntu and mint?
Mint actually uses Ubuntu's repositories for most of the packages you'd install. So, outside of the things which Mint specifically overrides in their own repository, Mint is Ubuntu.
You can find what software Mint itself provides here: http://packages.linuxmint.com/list.php?release=Rosa . As you can see, most of those packages are related to the display environment.
The main difference that I see is that Ubuntu is owned by canonical. There is some paid developers in charge of packaging some programs when linux mint is supported by the community. As always community based project are less subject to bad direction that can be taken by a company...
Mint had more proprietary codecs installed for audio and video. I believe this is no longer true in modern versions. I think it still comes with more pre-installed software than Ubuntu. Also the Mint trademark is owned by the linux foundation, Ubuntu by a non-profit.