I reached out to someone who has successfully cohabitated bearded dragons and they said that this would work out fine. They also recommended having another temporary enclosure on hand just in case they become aggressive. If you did decide to try this they would need plenty of climbing branches, basking spots, hides, other ways to get out of sight from the other dragon, etc. If you added multiple basking areas made of slate they would likely get enough UV.
Of course if you don't want to do this you don't have to. But I personally recommend it since they can learn from each other and interact. If you decide to try this I would recommend the 3' high cage.