If you have to ask you shouldn't be looking at Ubuntu Mate. It's not a beginner's operating system.
I will have to disagree Dougie.
Ubuntu, Mate, Lubuntu are beginner's OS or more correctly users OS's.
They are for someone who just want to write docs, surf the web, watch youtube etc.
Perfectly fine to swap for the wife's PC, to finally get rid of Win10 in the house.
Lubuntu is smaller than Raspbian too.
Raspbian is more a tinkers OS, can make LEDs flash etc.
But latest Pixel desktop has just pushed it over into a pretty Desktop as well.
It does come with the kitchensink, great for coders.
If the user does not want to do anything with the GPIO pins or code anything then Mate etc should be ok.
Simple for a user to decide, get a bunch of SD cards, put different OS on each one and see which one gets used the most.
And keep trying new ones every few months as they get better etc.
With the Pi's you don't have to settle for just one OS, you can swap OS faster than just about any PC.
I ended up with a box of SD cards and writer that I carry everywhere.
That said, I'll take nominations for 64bit OS's.
I'm still waiting for a good 64bit Desktop OS, bring on 4.8.x
Fedora 25, Mint 19?
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges