I always appreciate a good salesman...I have been in sales for 10+ years...I like your attitude... If money was no object I would buy one of each but right now I can just afford to get one.
he's saying that if you buy the G27, you can also add a 40-9mm conversion barrel and mags and shoot 9mm out of it.
You'd have both
Many of us choose the G23 over the 19 for the same exact reason.