I just hung some panda in my grow room, and having helped a buddy hang Mylar a long time ago, something should be said for convenience. Unless you a have a second set of hands, Mylar is a royal pain in the ***, while Panda can be hung with relative ease. If your space is small, like a closet where your Mylar cuts will not be very big then go for Mylar. However the room I just hung the Panda in (by myself) had walls 8' long, 7' high, and to get that up solo was great, I would not have been able to get (and drag) around Mylar in that way, Mylar is more prone to tear.
Also you can clean Panda, where as Mylar is hard to clean, if you can even clean it at all without damaging it (depending on what you spilled/flung on the Mylar). They do make a thicker kind of Mylar though, that I have not tried, the Panda I had was at least 5x the thickness of the Mylar I had experience with.
Just some thoughts.