Someone in a thread somewhere said that:
JS Guards: Trains JS fastest of the three alternatives
JS Wingmen: Trains JS a bit slower but trains IS as a bonus
JS Forwards: JS slowest but as a bonus adds all of the secondary training. But a slight lower training speed at those to.
To bad i couldn't find the thread though.
However, it seems that JS for wingmen doesn't train IS at all. Which means that other skills which are trained along with JS for guards and wingmen are the same (JR, DR, HD).