I know it's personal preference and subjective, but what 9mm is widely considered as the best CCW and why?
I've never been a huge fan of 9mm, but considering one mainly because of how much more inexpensive the ammo is !! It's considerably more inexpensive!
I think 9mm is so popular because it offers a nice balance between power, recoil, gun size, and gun weight. Especially with options like the PPS and Shield, 9mm seems to be
the sweet spot for discreet defense. Having experience with both, I prefer the PPS 2:1. It fits me better, I prefer the trigger, I really like that style of magazine release, the fit and finish seem a tad nicer, and yes, it is prettier.
You say that you've never been a fan of 9mm and some people aren't. The question is "why". While more powerful than ol' .38 special and smaller cartridges, some people just don't think it's enough. Some of these people prefer .40, which is available in a lot of the same platforms but at higher ammunition cost and more recoil or muzzle flip. You've got to ask yourself if you are personally comfortable relying on 9mm.
Like in so many other questions, use is what matters. Obviously, any gun you carry and trust with your life should be one you've practiced and know well. Will it be a primary range gun that you shoot for fun? I ask because it seems ammo cost is a primary driver in your reasoning. How often will you actually be shooting it? Also, will you be carrying it with premium defense loads? If so, how much practice will you be getting with those?