Teardrops n Tiny Travel Trailers

My trailer is here and I will be picking it up, probably Monday or Tuesday. I was going over my plans/ideas (again) and have a question on insulation.

At Home Depot (in Canada), the rigid pink or blue extruded/polystyrene foam insulation that many here use in their trailers, is almost 2x more then the price of Plasticspan inslulation and seems to have a slightly has a higher R value then the polystyrene type for the same thickness.

As my 6x10 trailer is small, the cost difference is not enough to worry about between the 2 types, however I wonder why people choose the blue or pink poly type of insulation and if there is any real difference when used for our purposes?

The material that you're looking at is a Canada-only item, rated at R3.75 for 1" thick. This pink stuff from Home Depot is rated at R5.0 per inch:

http://www.homedepot.com/h_d1/N-5yc1v/R-100320343/h_d2/ProductDisplay?selectedCatgry=SEARCH+ALL&jspStoreDir=hdus&superSkuId=202938960&catalogId=10053&navFlow=3&keyword=r5+foam&Ntpc=1&langId=-1&Nu=P_PARENT_ID&storeId=10051&Ntpr=1&ddkey=Search

The only plus to the Canada stuff is that on the manufacturer's web site they claim the gas used to make the bubbles is air, and it won't degrade in performance over time like other stuff. Note that the pink stuff in the link above specifies that it is guaranteed to retain 90% of its advertised R value over time.....

That pink foam insulation does not look like the same we have at the Home Depot here. I will double check the next time I am in the HD store and will write down the brand names and the respective R values again.