I have two of my favorite handguns that seem to get carried the most...a Browning Hi-Power in .40 S&W (nicest gun I own!!!)...which seems to get carried the most and a Sig 226 in .40 S&W that is my second fav. I really do like them both as much as any gun I have every handled or owned. When I need a smaller carry gun I steal my wife's Kahr CW40 in .40 S&W...which is quickly becoming a favorite...may have to break down and buy one for myself.
Most important...find a gun that fits his hand well and one that handles well for him. Then shoot it regularly...a lot!