Although the Nether Dragon was easily set ablaze, the Nether Dragon Formation wasn't limited to a single point. It was far more flexible than the Celestial Dragon Treasure, but it lacked a bit in raw power. Its current state was already its limit, and the consumption was staggering. At most, it could only control one Nether Dragon; any more than that was impossible.
As for the Celestial Dragon Treasure, anyone it acknowledged as its master could control it. As their cultivation level rose, they would be able to control even stronger Celestial Dragons.
In terms of tier, the Celestial Dragon Treasure was undoubtedly far superior. The only issue was that it was extremely difficult to control. If it didn't acknowledge a master, it was completely useless.
