My personal favorite advantage of Minetest over Minecraft is the larger world height. Minetest's worlds are 62000 blocks high, compared to Minecraft's 384 blocks.

You certainly don't need most of those 62000 blocks, but 384 is quite limited, especially with only 128 underground. It means that Minecraft's caves are all rather flat and there's practically no challenge in getting to the rarest minerals.

With Minetest, it's actually worth going down the more vertical caves rather than just digging, and it's worth building intermediary bases. Minetest was the first time I felt minecarts and ladders were useful while mining.
It makes mining challenging and fun, even without mobs.