A number of years back when we resided our home, it involved a total strip off of the old Louisiana Pacific siding (the stuff that failed and was the subject of a major class action). We replaced this with Hardi-plank. I also took the added measure of installing a Reflectix double reflective insulation layer beneath the Hardi-plank (it was an approved Hardi underlayment and also served as a vapor barrier). Another plus was the contractor said if we bought the product he would install it at no additional cost as he was planning on the labor for a vapor barrier in the bid already.
After it was installed, we did notice a couple of things. The house was quieter overall with less outside noise making it inside (some of this is probably due to the density of the Hardi-plank), and it seemed to hold heat/cold in better as our utility bills went down about 15-20% on average each month. So in my mind the double reflective insulation product did make a difference.
I presume this is the same sort of product that Coachmen uses in their "radiant barrier upgrade", do depending on the increased cost of that package, I would think it will make a difference.
Another thing I learned. I had some of the Reflectix left over and in my previous trailer I made cutouts to friction fit in the overhead fan vent and window openings for added insulation and daytime sleeping (it blocks 100% of the light). Windows in my prior trailer were the main point of thermal shift, so that friction fit insulation in the interior of the window frame did make a difference. Of course you can't see out the window then, but for storage it also kept out the UV and prevented fading of the interior.
So I would probably consider it if I was buying new, or it was on a unit I was looking at (consider it a plus).