Actually called, Rustoleum, Friday, and ask that same question on the "stops rust label" products
Answer is the professional contains more curring agent than the regular, which means it cures faster than regular.
Also the spray can is available in Professional label, but have not been able to locate.
All oil based alkyd paints will oxidize with time, it starts oxidizing as soon as it is applied.
Applying a clear coat will prevent the color coat from oxidizing.