Chain drive - most efficient, most maintenance
Belt drive - not quite as efficient, not much maintenance
Gear drive - least efficient, almost maintenance free
Chain drive most efficient? You sure? And why would a belt, which has no moving parts, be less efficient than a chain, which has what...216 moving parts for a 108 link chain? And all those moving parts, the rollers, lose efficiency the second they do their jobs, i.e., roll. Since there is no "perfect" lubricant, those rollers are never rolling at 100% efficiency and even freshly lubed, they lose efficiency with every pass over the sprocket until they need lubing again, which only restores their efficiency to a fraction of their "new" efficiency level, and degrades quickly 'til they need another lubing again.
And besides the lack of moving parts with the belt, which essential needs no lubrication, or can be considered "self lubricating", isn't the stress friction, basically the contact point between the drive medium and the drive and driven pulleys, spread out more with a wide belt than a narrow chain? I'd love someone to calculate the PSI of a 1/8" wide chain roller at point of contact with the driven sprocket and compare that with the contact PSI of a 1 inch wide belt contacting the driven pulley of an equally weighted and powered motorcycle under similar acceleration.
Gear drive - least efficient. Yep. Almost maintenance free - man, you need to define "almost". If almost means maybe once in a million years, I'll give you "almost maintenance free". Otherwise, it still beats hell out of a chain, but doesn't really surpass a belt.
Finally, so as to not beat this to death with opinions, which of the three would you prefer replacing when/if they go **** up? A chain, along with its countershaft and rear wheel sprockets, a belt with same, or a driveshaft, u-joint, pumpkin, ring and pinion? Factor in cost and labor.
I figure a belt wins. Costs pretty much equal to chain, but no special tools needed to install.
Oh, one final + for a belt over both chain and shaft. Much, MUCH quieter. Never heard a belt grind like a chain or whine like a shaftie.