Entire books have been written on the characteristics of various film supports. I review the pros and cons of CTA (aka acetate) and Estar (aka Mylar or polyester) in "Making Kodak Film". Briefly: Estar has superior dimensional stability and physical strength. It has a memory so it can severely curl in roll film applications and also it light pipes causing fogging. Estar does not out-gas so it can be used in the vacuum of outer space. CTA has little memory so works well in roll film applications.