Timing belts are statistically less trouble than chains. Chains contain hundreds of moving parts that wear, causing the chain to "stretch", causing valve timing to change. Belts suffer virtually NO timing change and no stretch in their lifetime.
Anyone who has owned a 2600cc Mitsubishi engine (used by Chrysler in their older minivans and K cars) knows how much trouble timing chains can cause.
The biggest problem with the 8r/18r/20r/22r toyota engines as well as the early M series engines was their timing chains and tensioners.
The later A seies engines, as well as the M G twin cam series with belt drives were virtually trouble free. Chains are very sensitive to lubrication. Belts require no lubrication.
Belts are also more efficient at transferring power than regular link chain - not any better or worse than "silent" chain - which is a lot more expensive, heavier, and more complex AND EXPENSIVE. For overhead cam engines, it is pretty hard to beat a properly designed and implemented belt drive.
The complexity of a chain drive on an opposed overhead cam engine like a Soob can introduce a LOT of new failure modes - I would not be surprised to see the chain drive "experiment" end up being short lived
- with a return to belts within a couple years.