If Minecraft had only one biome and you had to build in it and work with it, what one would you choose? Explain a little about your choice and why it works for you.
Since there are 36 or more basic biomes at this point, I don't think a poll is necessary, or wise. Please pick just one, and tell us why it's the best.
Savanna is right for me. (Surprise! I bet you thought I was going to say, "Nether")
It has excellent starting support right out of spawn: reasonable wood, access to water, grass for seeds, and a high village spawn chance. There are plentiful animals, including horses if that's important to you.
The geography of savanna is excellent for building: wide flat plains studded here and there with reasonably high, flat-topped hills. The savanna M biome is rare but creates the most dramatic, highest spires in the game. Less terraforming needed = more time for building.
No lightning strikes to ruin your day or set things on fire that shouldn't be. No variant zombies to cut into the total number of zombies available (no husks, etc), giving you the maximum shot at a zombie villager spawn so you can enrich the villager mix you have.
The cons are pretty low-impact. Orange wood doesn't really bother me, and as long as there are a few oaks about, I can grow these to get apples and non-orange wood as needed. The grass colour is not the brightest, but I think all things considered, it complements the other colours in the savanna well, and allows you to detect creepers from a distance. No rainfall might bother some, but remember that fishing bonus applies whether there's drops in the sky or not; and frequent rivers crisscrossing the Savanna mean you can still build near one and get all the raindrops you like.
Lastly and perhaps most importantly, savanna does not produce birbs, ocelots, or wolves. For big fans of tameable pets, this is probably the deal breaker. I can't answer that, but I don't personally care for the pet mechanic in the game, so not having these available doesn't hurt as bad.