“Beware the man with one gun, he knows how to use it.”
I've seen that many times and it is BS. Everyone I know who only owns one gun doesn't know squat about guns. I recognize this may not be true for every person who owns only one gun, especially for someone on a budget.
I personally like variety but I don't consider all my handguns as self-defense guns (though they could all be used that way). I like single action semi-autos best but I have striker fired (with no thumb safety) and traditional DA/SA. I like steel revolvers but I own one polymer revolver. I'm not much for lasers but own one handgun with a laser. When it comes to carry/defense, however, I stick to a gun that is point and pull the trigger or with a frame mounted safety (down for fire).
Really, though, it's just a personal preference. If you want to stick with a particular manufacturer and type of gun, nothing wrong with that.