What is the difference between Remington STS shot shells and Winchester AA shot shells?

I am reloading for trapshooting and I was curious if there was a difference between STS hulls and AA hulls. I have heard that there was but I don't know what the difference is. I would like to know soon please! :-) thx
Update: what i really want to know is if i can load STS hulls the same as AA hulls if there is a large difference between the 2 to throw anything off
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