hey, i would recommend panda film. it lasts longer than mylar and ends up being more reflective over time (mylar looses reflectivity fast) and you can wash it after a run and its almost as good as new. so from what i've seen this:
its lasts longer
its more reflective over the long run
its more durable
you can wash it
cheaper than mylar (for me anyway)
i'm paying like 1$ per 1' of a 10' wide roll
hope this helps