[Sailor Steve]

I don't know if the government's hiding something...well, the government's hiding lots of things; I just don't know if they're hiding aliens.

Do aliens exist? As has been said, the universe is a huge place, and it would be silly to assume they didn't. Are some of them more advanced? As Skybird pointed out, it would be arrogant to assume otherwise. This also holds true of the question of whether they are significantly different. The only possible answer we have at this point is "I don't know." Speculation is fun, but without any real data we can't tell anything.

My philosophy is: When they come knock on my door I'll be more sure. Until they bother to do that, screw 'em.