Most insulations will work great in an RV. You'll want to look for the R-value of the insulation as well as any other properties it has.
For instance, our Heat Wave Pro has 3.91 R-value but because of the two layers of foil surrounding the jute insulation, it easily reflects radiant heat, making it better insulator against heat.
We like to combine Heat Wave Pro with Damplifier Pro to get the added sound benefits from dampening the structual noise AND resisting thermal transfer through the sound deadening mat and foil.
You can also use UltraTouch denim insulation for another fiberglass-free alternative. At the end of the day, it comes down to how much insulation you need and how much you have in your budget.