They both have the same r-value. Just one is fire retardant and the other isn't.
I just couldn't decide if it made sense to worry about fire retardant foam. My thinking was that with the metal barrier on the outside, the only way the foam catches on fire is from a fire thats already on the inside of the bus.
From what I can tell looking through build threads, no one is worried about their insulation catching on fire. Just wanted to check before buying...