Theta is a creative world made for greens, so map-making would be easier (and wouldn't take months to gather materials).
Specifics about Theta World
Theta is a creative world, which can be warped to with /warp theta for green or higher ranks. The world size is 12k on all sides, though players cannot currently build past about 7000 blocks from spawn. Theta is generated with a normal minecraft seed, namely from version 1.12.2. Despite the world being from 1.12.2, blocks and features introduced in later updates can still be used.
Maps that are currently in Zero will stay in Zero, unless the map creator wants to make changes to them. A player can request for a map transferred from Zero to Theta. Because of the creative addition to Theta, the required quality of map aesthetics to be acceptable for FFA has risen.