Most knowledgeable folks (not me or you)..people like the elite militaries, and police all over the world would say nothing equals the 19's reliability. So that's not me saying it.
While, indeed, the G19 (and most Glocks) are indeed ultra-reliable (I carried the Glock 23 as my primary choice for civilian carry for at least a decade), and the Navy SEALS and Special Operations community have gravitated toward the Glock platform (almost certainly due to cost and weight beating the P226), that does not mean that it's the best choice for a low-skill civilian. I like striker and fired about equally well, depending on platforms and scenarios. I carry both with total confidence.
I have a very large assortment of roughly a 50/50 collection of striker and hammer guns, have significant personal and professional shooting experience/training, and have trained many people on shooting. I rarely steer new shooters to striker guns because I think they require a higher skill set to avoid having AD/ND. I strongly urge people toward hammer fired guns because of their inherently safer designs with more intuitive features.
Yes Glock is an absolute beast of reliability. I don't think I've ever seen a malfunction. Having said that, I could say the same for others makers, including CZ and Sig Sauer, and only seen 1 HK malfunction. So there's 3 hammer fired options (the Sig P226 was the Special Ops sidearm of choice for decades), that are ultra reliable and durable.
I generally think the 9x19 is the minimum ideal caliber for self defense, but having said that there are situations where 9x18 (Makarov), or 9x17 (.380) or even .22LR is sufficient and better than nothing. It's not my preference, but hey, I'm generally just happy if someone finds something that works for them. I've met folks that confidently carry a Walther PPK, Bersa Thunder, or Sig P232 in .380. To each their own. I have handguns in .22LR, .380, 9mm Mak, 9mm Lugar, .40 cal, .45 acp, 7.62 Tok, .38, .357 mag, .44 mag, and probably others. They'll all get the job done, ultimately, if the shooter is trained and does his part. I have my preferences (power vs. capacity vs. size, ease of use, reliability, etc.), but I'd carry almost anything with confidence it would defend my life pretty well. People tend to not like getting extra holes put in them, regardless of size.