<I tend to like metal more than plastic, but would it help with reliability, longevity, or accuracy in any noticeable way?>
There's nothing wrong with the plastic rod installed by CZ. I've not heard of any failures of the plastic rod.
There's the placebo effect that sellers of these rods hope you get. You buy it, you believe it will make your gun better, and it may have a metal effect. Of course you've been relieved of some money as well.
There's the "group think" mindset as well. If everyone else has a metal rod, you've got too have one too. If the big boys have them (and sell them) why, it must be good!
In this case this is a solution in search of a problem. It's your money and there's always someone hoping to make it disappear and reappear into their pockets.
AFAIC, after-market metal guide rods for CZs fall into the category of shoe-string stretchers, sky hooks and Flying Spaghetti Monsters. YMMV.
Steve