Actuallly, gears are more reliable than chains...ever heard the old joke
Knock knock...
Who's there?
Honda camchain tensioner...........
Chains sap less power than gears,
I'd imagine belts less so still
( Lower reciprocating mass..... )
Noise levels for belts are also lower than chains or gears....
My Guzzi had a gear driven cam....what a wonderful noise that made