Hi.
Timing chains or belts are pretty much the same. I don't think one offers another advantage over the other. The timing chain is less maintenance because usually, it doesn't skip/break/whatever. However, just like all chains, it must be tensioned. So the engine has a chain tensioned to cope with the slack that occurs over the life of the vehicle. That's why you never see chain replacement intervals for chain driven cars.
However, that's because car engines sold to consumers simply do not induce enough stress on the chain. In high performance engines that operate in strenuous conditions and at high speeds, chain tension is difficult to consistently maintain. That's why they must be manually adjusted, and usually after a race or whatever, they must be replaced.
Timing belts are the same. They still use a belt tension device and have teeth to accurately time the turn of the camshafts. Usually, a belt doesn't break with today's materials...it usually skips or hops due to worn materials. With today's materials, belts actually don't stretch per se, if you think they do. They act almost like chains in that regard. However, they also suffer the same high speed problems as chains.
They are two ways of going about turning the camshafts. One is not superior than the other. If an engine suffers major damage because of a worn timing belt, that's the engine's design fault and lapses in the owner's failure to properly maintain their vehicle. It can happen with a chain as well. However, chains given more confidence because they are less likely to skip a tooth. However, superior as it may look, the chain system is only as good as the oil that's placed inside the engine. Since the chain is lubricated by the engine oil, if the owner fails to change his or her oil at reasonable intervals, engine problems can result.
So, I really think they are the same. Most of my cars have belt driven camshafts, and my Elise and ZX-10R have chain driven camshafts. I tossed out the automatic chain tensioner in my motorcycle after it failed to properly time the camshafts. This was probably due to the power output and increased engine speed that resulted from an engine rebuild. The Elise has been ok, but it has too few miles on it to say. I replaced the belts on my Tacoma and MR2 every 100,000 miles.
I like the idea that I can have a fresh belt instead of a used chain.
There isn't any sludge anywhere else that I can see.
