I'mma jump aboard the 3.5-era Dragon bandwagon.

I know, you all expected a Lawful Evil Outsider, but let me explain a few things.

One, several Dragons gain the Alternate Form ability, which means the ability to pass safely among mere mortals. As fun as it may be to lord my vast superiority over them, sometimes it's nice to not be a perpetual spectacle.

Two, flight. Worth expressing, but most Dragons gain the ability to fly under their own power, which is just legitimately awesome and great.

Three, Sorcerer casting. In addition to their SLAs, Dragons can learn and cast spells as a Sorcerer. So, you know, free spellcasting on top of all the other cool stuff.

Four, immortality with limits. See, various Outsiders can do all the stuff I just mentioned, but they are immortal in a pretty solid sense - even if you kill them, they will reform. Not so with Dragons, who - as has been mentioned - can age indefinitely, and grow indefinitely, but are not immune to death.

I would totally love my nigh-omnipotence, s'true. But if ever there came a day that I grew weary of this world, it would be good to know that it's a playground, not a prison. As an Outsider, I'd be stuck in the same cycle; as a Dragon, I would be in charge of my own fate, right up to the very end. And that's a liberating feeling.