It’s mostly an aesthetic choice, a choice between desktop environments.
Desktop environment (DE) is just the visual bells and whistles that you use to navigate the PC, like that quick animation when you minimize or maximize a program (Apple loves this), a start menu that has cute icons for each program and turns blue when you pass the mouse over it (or a start menu that is just a raw list of program names), etc.
Mint Cinnamon uses a DE that looks like Windows 7 reborn, Mint XFCE uses a DE that looks like Windows XP reborn, and Mint MATE uses a DE that looks like Windows Vista reborn.
People will tell you that these DEs will have a slight difference in consumption of RAM, where the most ‘shiny’ DEs will consume more RAM (XFCE
That is the true beauty of FOSS technology. Even if it fractures into regional forks, Linux code is open and free (as in freedom), so each fork can just copy-paste and compile the changes made in others if they advance the tech forward, no direct cooperation is actually needed (if everyone keeps publishing its works).