I would honestly follow where your community/friends are at. The minecraft modding community is extensive and amazing at bringing endless experiences to you, and the amount of active playthroughs willing to accept new members is likely higher on Minecraft than Minetest instances.

However, if you wish to develop and mod yourself rather than play on pre-existing modded and vanilla content, I could see some great experiences from joining a community on Minetest. But to me, Minetest is a development and educational tool, not a game.