Hello John,
There are 3 kinds of Stromtroopers a RS kit could make out of (well 4, if you count a Sandtrooper)
- ANH - Stunt Stormtrooper
- ANH - Hero Stormtrooper
- ESB Stromtrooper
The basic difference between an ANH "Hero" and "Stunt" is the helmet (and the ammo belt config). You can check the CRL for a detail breakdown on the differences.
https://databank.501st.com/databank/Costuming:TK_anh_hero
https://databank.501st.com/databank/Costuming:TK_anh_stunt
One way to look at it, "Stunts" are the normal average Stromtrooper you see marching on screen, in numbers. While "Heroes" are Han and Luke in Stromtrooper disguise aboard the Death Star (although you will see Hero helmet appears here and there during the film).