The answer to that question is.............it depends on what you are using it for.
Both are transparent plastic so if all you are doing is using it as a measuring devise then it's six of one and a half dozen of the other.
The Epson transparancies you run through a printer for transferring designs.
Acetate can be used for transfering designs by scratching the design into the sheet, rub some black into it and transfer. You can't do that with the Epson transparancies because the plastic is too soft and won't create the essential bur that acetate gives.