Morgoth v. Sauron

[obloquy]

In a nutshell, Morgoth had become much reduced because of the way he chose to disperse his power -- in creating things and corrupting things. Sauron, on the other hand, worked differently, and actually enhanced his own power. The division between "orders" of spirits is not actually as large as it might seem. Tolkien also said that Glorfindel, after being reincarnated, had achieved a potency of spirit possibly on par with that of a Maia.