I would love to carry a PF-9 except that I've heard sooo many stories of them having feeding problems and ejection problems. I wouldn't be able to trust one without putting several hundred rounds through it. The problem is they're so tiny and seem to wear out and break after awhile, so by the time I was comfortable that it was reliable ... at that point I would be worried about wear issues. On top of that, the PF-9 is simply not a comfortable gun to get any range time with.
A Bersa is a very different gun, but if you're going to compare the two, the Bersa is reliable, has a comfortable grip, and is actually fun to take to the range.
There's no free lunch. That's why you see a lot of people who use the relatively thick Glocks and XDs, or the slightly smaller Kahrs. You have to be confident in what you use. Personally, if I wanted something smaller/lighter than my Glock 26 I'd have to go with a S&W J-frame.
Am I being reasonable? Probably not. I'm sure the Kel-Tec would work fine 98-99% of the time. Your chances of getting in a situation where you needed your gun, and then having a Kel-Tec malfunction are certainly less than your chances of getting killed by a drunk driver or some other freak accident. But if I carried a PF-9, I would always have those failure stories in the back of my mind.