Timing gears are the most ideal, since all they need is periodic alignment.
But between chains and belts, I personally prefer belts. Their built-in obsolescence makes a car owner exercise due diligence in replacing them at specific intervals. Much like engine oil, it pays to keep certain engine parts fresh.
Timing chains are more durable (they're largely safe from the effects of heat), but they're not indestructible, as they're prone to stretching over time. This can have adverse effects on camshaft timing. Some motorists rely too much on a timing chain's vaunted durability, when it should still be inspected periodically.