That is a valid argument as well. There are no wrong answers for this. Unless you have no ammo at all due to not following the 5 P's.That's certainly a viable solution, especially when you consider the amount of ammo you can buy with the price of a gun in another caliber, but everyone's needs and desires are different and that's a good thing (at least for experimental purposes). Most of my carry guns are 9mm's, but I like having at least one of all the popular calibers for a host of reasons which may or may not provide a significant advantage at some point (or disadvantage). One, I am a curious person and just like comparing calibers (hence I can shoot 9mm, .40, and .357 out of the same P229). It allows me to be more intimately familiar with the various caliber & loading choices out there for my own knowledge & experience. Even some very unlikely scenarios such as bartering with someone who doesn't prefer or own 9mm in a SHTF scenario could potentially be of value. Hopefully having to use ammo from any caliber to defend myself will never come to fruition, so I guess we're always dealing with highly unlikely probabilities when you think about it, which is why both approaches are truly valid. I also like the fact that it takes the edge off. You may not be this way, but I know I am personally less defensive about discussing the caliber debate because I have guns in various calibers (especially my favorite gun). I also like the fact that it keeps the door open in many ways. For all we know in five or ten years technology and/or marketing will make .40 S&W, .357 SIG, .45 ACP or something else reign supreme over 9mm again. As such, at least for me, it would soften the blow having guns either already chambered or readily converted to what the next "best" caliber might be at any given time. For example, I know I have had the same thought as others that perhaps .357 SIG might be rebranded as 9mm Magnum (losing the deceptive diameter designation of a once ideal caliber and instead relate it to 9mm Parabellum since both are 9mm bullets). Perhaps 9mm Short might regain its popularity since people are overwhelming carrying semi-automatics in lieu of the .380 ACP's namesake the .38 Special). In any event, I can see the value of putting all my money in 9mm or using some of it for a variety of calibers. Both approaches are perfectly legitimate in my opinion.
I like too many calibers as it is. Reloading makes it very easy to add another one to the inventory. Too easy.
Great looking Sig BTW. Really gorgeous.