Minecraft wiki entry for Best_biomes_for_homes, associated text: Mycelium, on which you can plant mushrooms independently of the light level, like podzol. Contrary to podzol, though, the mycelium will spread like grass, making it easier to obtain in large quantities.
Red mooshrooms spawn here, and give a reliable infinite food source, as long as you have bowls in stock.
In Java and Bedrock editions, when mooshrooms breed, they have a small chance to spawn as brown mooshrooms, which if milked after being fed by flowers will give you suspicious stew that can inflict you with status effects depending on the flower used. Red mooshrooms also transform into brown mooshrooms when struck by lightning and vice versa. If you shear a red mooshroom, it will drop a few mushrooms and turn into a normal cow.
Small and large mushrooms, both types(red and brown), spawn here, allowing for more mushroom collecting and using the mushroom block as a building material (if you have a Silk Touch shovel).
No hostile mobs spawn within this biome, which means an overall safer experience.
Offers an interesting aesthetic to build structures surrounded by huge mushrooms and mooshrooms.