As far as what "I" was told by ----------> Valmet, the difference between the 412's and then the "S" model was, the "S" model has a slight difference in how the fireing pins work, "rebounding" is what i remember. I think that's all the real difference is between them, besides the difference in the wood and finish.
The triggers are the same single trigger with the same double trigger option...
I'd keep what ever one you like better...
The ST was the trap model, it had a higher comb/different fore end, a different safety design and "trap" bbls...
DM