Could someone provide a comparison between having a bike with a chain, with a shaft drive and with a belt drive like the Gates Carbon Drive?
It could be good to know who fares better in terms of low maintenance, durability, and efficiency.
For fixed, single speed and hub gears belt drives are great, if slightly more expensive initially. They don't work with derailleurs.
The key difference is that as chains wear they also wear the sprockets and chainrings and therefore all need replacing if you leave it too long or don't lubricate often enough.
Belt drives are used in many applications which are harsher and less maintainable than bike drivetrains - 70k Miles @ 3000 RPM for a car cambelt should give you confidence to fit and forget a belt on a bike. Also used on big motorbikes (Harley, Yamaha, Buell) as a chain replacement.
Shaft drive is too inefficient and heavy for practical use on a bike.
I have both chain and belt drives on different bikes - they do different things but are both fit for their respective purposes. The chain needs lubricating frequently and replacing from time to time. And the belt-drive simply doesn't.
Wow, this discussion really highlights how bike cultures can differ across regions, I'll try to stay as objective as I can.
I have an 8 speed hub, with a conventional chain, I do about 150 km pw. My chain will be useless after 8 months, and probably would need replacing after just 5 (I just don't get around to it till it's really bad). Problem is, I can't just replace the chain, the front and rear sprockets need replacing too, and the wear also damages my hub. Once you've paid for all that (including labour) the economics swing in favour of a belt drive, which I can replace myself, and it doesn't require new sprockets , which will usually outlive the belt by several times.
Bike radar did a pretty good article on this, which you can find here.
My personal opinion is Carbon Drives/Shaft drive are quite fancy but pretty useless. They are more expensive, require specific frames which are usually quite expensive, and their try to solve a problem that simply does not exist. With a carbon/shaft you can only run a single gear hub (maybe with internal gears, but that's not the point). A normal bike chain lasts a few years in mountain/road riding and keep in mind rear derailleurs play a huge part diminishing a chain life. On a single speed bike the chain pretty much has no wear and just lasts and lasts.
Regarding maintenance, if you live in a dry climate, the oil on the chain will last a few months, and if you constantly ride on the rain I don't believe you don't have 20 seconds per month to spray it with a good oil. Because that is all it needs.
I do have a bunch of cheap (around $150) single speed bikes with chain that have been working perfectly for a few years with once a year maintenance.
Please keep in mind this is an opinion assuming money is a conditional when searching for a new bike. i.e., I am saying that for practical purposes, when you justify them comparing features and price, chainless options are not worth it. In the same it is not "worth it" to have a Ferrari, even though I sure would love one in my garage.