Closed cell vs. open cell foam

[verizon6000]

I am foaming my exterior 2x6 walls. I have quotes from open cell and closed cell applicators. Which would you choose and why with no cost factor involved?

[tooltroll]

As I understand it, closed cell is denser and has a higher R value, since the gas in the cells can't migrate from one cell to another.

[David]

I thought closed cell applications have less pollutants released into the air (for the same reason).