Back when I competed, I loaded my own ammo, and did so for several years after I stopped competing. In that time, I loaded many thousands of rounds on a Dillion press. I had one squib in those many thousands of rounds. Other than that, no problems.
I have had at least five complete dud factory pistol cartridges. I found a single 9mm round in a freshly-opened box of WWB .40 rounds (quality control at a major manufacturer, eh?). I have had factory .223 rounds that didn't have enough juice to cycle my M4gery.
I don't believe for a second that factory ammo is any more reliable than good handloads/reloads. My experience shows that it is actually less reliable than reloads.
However, I have always carried factory ammo, anyway. I am an LFI grad, and what Mas Ayoob actually says about factory ammo is that (a) an overzealous DA can distract a gun-ignorant jury by implying the defender made special loads designed to kill and maim, and (b) that the defender may need "exemplar" loads for the forensics people to use when recreating the shooting, which is much easier with standard factory loads.
I do not doubt at all that (a) can happen. Look at the hysteria among the gun-ignorant about "assault rifles." I am not certain about (b), though the case discussed in this thread is an example that Mas has used.