Is higher density a reward?

[anagogy]

Is a higher density reward for living a good life? For those who are polarizing positively.

Or when we're there will we see 3D was a reward for having priority in harvestability?

It could be looked at as a reward, but no one is dealing out the rewards, it is more impersonal than that.  Your plane of existence is a function of your consciousness level.  When your awareness stretches beyond the continuum that you presently exist in, you gravitate to a new space compatible with your consciousness.  Like grades of oil in a glass.  The less dense fluids float up.  It also depends on what you want, the STS love the outer tangible world.  The STO tend to desire more inner spiritual pleasures.