Good or Bad...?

Okay well the question i have is how do you know what to use if tin foil is terrible and mylar is good... like there both in general the same thing how do you tell which reflective thing like that are good..?

Might be because mylar tends to hang a little straighter than foil. You cant help but crinkle foil up some and that creates the hot spots. I could be way off here, but as high as I am right now, it makes perfect sense.

OHH MAN ME TOO BUT OFF medical blow... but i also heard it helps to crumble that shit up cause the light and cocuss in one spot because it reflects eyerwhere..