Putting aside gear-driven timing designs... I'm of the opinion that there's a case to be made for both belt-driven and chain-driven timing drives.
One can list countless engines that employ timing chains that suffer practically zero wear during their life, and vice-versa. Winners:
The original Ford modular engine, both the SOHC and DOHC. Very rarely do you hear about one of those failing.
Northstar engines. Head gaskets, sure. But timing chain issues? Never.
Chrysler 3.7/4.7. Again, plenty of other issues but timing chain isn't one of them.
Nissan VQ. Never an issue.
Then, you have the problem children... The aforementioned Ford engines, VW 2.5 I5 and VR6 engines, MB engines, etc.
Same goes for timing belts, though. A Honda J35 belt can look beautiful after 150k, whereas a Subaru EJ25 belt will look terrible by 80k. Not to mention, the J35 belt is puny compared to the EJ25. One need look no further than the amount of tension on the belt combined with both the routing and radius of bends a given belt endures to establish a reasonable conclusion: length+tension+flex=failure.
Using the J35 vs. EJ25 example: the J35 belt makes 6 bends in total. Crank pulley, idler, front cam, water pump, rear cam, tensioner.
The EJ25 belt, in comparison, makes 8 bends. 90% of which are MUCH tighter than anything the J35 sees, leading to advanced wear.