First, nitrocellulose is unstable to some extent and subject to attack by many agents. See this: http://sciencelinks.jp/j-east/articl...03A0122159.php for a minor comment on the fact.
As for uses of acetate and polyester as film supports, there is a degree of dimensional stability gained with polyester, along with increased expense, so it is used on sheet films. The most prominent use was in dye transfer matrix films which must be exceedingly stable to changes in size. It is also used in the printing industry.
There is a difference in static electricity build up, coatability, and tensile strength. Thus, you can coat on triacetate with a solvent wash and then the emulsion, but polyester requires pretreatment with a corona discharge before it will accept a coating.
God forbid that a polyester coating jam in a coating machine let alone a high speed motion picture camera. I have seen high speed motion picture cameras with the sprocket gears broken off when the camera jammed while running estar based film. Same thing could happen in a film coating machine at high speed. The entire machine could be out of action until extensive repairs were carried out. The film just will not rip and therefore the inertia of high speed transport causes binds and kinks of 'an indestructable object' which then tears the machine up rather badly.