I have Mint17 and LMDE installed with almost identical packages. Both systems use similar disk space and RAM and they both run flawlessly so, for the end user, there is no appreciable difference. For the technical, Mint17 uses a later version of Linux and has frequent updates. LMDE use the Debian system of upgrade packages at 6 monthly itntervals. Debian is also slightly more difficult to install for the first time user.
I use LMDE as I see no need to have Ubuntu as an intermediary. As a desktop I use Cinnamon. There are other topics in this forum which you should read.
WHichever system you select, it will be the best Linux distro