When you say 03 and 06 you are referring to the 5903 and 5906?the 5906 is'nt the best full size 9mm for CCW.
the 03 model alloy frame is better suited. the 06 is built laike a tank, very safe pistol and more than accurate enuff.
also the squared off trigger guard is a skull-cracker if needed. try that w/a plastic pistol
Both of those had square trigger guards in the early production. SW stopped making the square trigger guard and 14 shot mags in 1991-1992 on the 5906 and 1991 on the 5903. For some reason the 5903 always came with a 15 shot magazine..as did all other variants of the 59xx series except the 5906 that started with a 14 round magazine until about 1991-1992. The blued 5904 is also an all steel frame but are much harder to find. (At least for me) Especially in very good condition.
Mike