Most of my carry guns are 40s&w. First and foremost, the 40s&w round seems to be more available in bad times, like right now. Secondly buying +p or +p+ 9mm ammo to get the higher power is getting very hard to do. Heck regular power 9mm isn't around these days, is it? It isn't on any shelves right now around here anyway.
BUT if you still want to shoot 9mm after buying a 40s&w, then all you need to do is buy a 40-9 Storm Lake conversion barrel for your 40s&w gun along with some 9mm mags. I have 4 SL conversion barrels I'm shooting out of various guns and have zero problems with them. I don't make a habit of carrying a conversion barrel for protection but after thousands of trouble free rounds I know that I could safely rely on them. Then to shoot 357sig all I need to do is change out the barrel to my 357sig barrels if that is the caliber in my safe at the time &/or I need the power of 357sig.
A gun that has the power that 40s&w offers and the capability of shooting several other calibers (9mm & 357sig), is a gun that even a newbie should at least consider before settling for a 9mm gun.