Fermentation Box Insulation Type? Fiberglass vs. Foam board

Hey Gang.... i'm thinking about building a bigger temp controlled fermentation box since i get maxed out with 2 carboys right now... I'm liking what TimWeber has going on with his build thread here . I'm thinking about putting the ale box on top of the lager box to save some space, and have door to each on the front. I'm seeing alot of people using the foam board type of insulation rather than fiberglass batting type. I was just wondering if the fiberglass insulation was not as good for this type of application, (2x4 frame box) or is the foam board just easier and it just comes down to personal preference?

Just curious...
Thanks gang..

Cheers...
Kyle...

You can find a comparison chart for various types of insulation here:

http://www.dannylipford.com/insulation-r-value/

The rigid foam insulation generally has a higher R-value per inch of thickness than the fiberglass batts. The advantage of using the fiberglass over the rigid foam in buildings is that it is much easier to install over irregular surfaces and it can be tucked into tight spots without having to custom cut pieces as you would need to do with rigid foam.