Torrent stats might be interesting - unfortunately, Mint don't appear to publish completed downloads from their tracker but just a quick check of the current stats on the 4 64bit 18.3 isos might be interesting as an indicator of the relative popularity of the 4 variants. Stats obtained via Transmission.....
Cinnamon - 4214 current seeders and 173 leachers.
Mate - 1308 current seeders and 45 leachers.
KDE - 917 current seeders and 29 leachers
XFCE - 800 current seeders and 28 leachers,
Just a note that I looked at this as I spotted the Cinnamon Iso on a torrent aggregator type site
in the top 20 most seeded torrents - just under Star Wars The Last Jedi....
Edit to add - worked out how to get the completed download stats from the tracker.....so just from torrent downloads the 64bit 18.3 isos have been downloaded around 340,000 times....
Cinnamon 18.3 64bit - 206317
Mate 18.3 64bit - 59787
XFCE 18.3 64bit - 40118
KDE 18.3 64bit - 31033