Interesting...
A chain sounds much better in principle, but we have had issues with our current 1.4 TSI Golf..
The dealer has told us that chains are prone to stretching on the older VAG 1.4 TSI units, especially if the car is left in gear while parked on slopes !!
Apparently, the 'Twin Blower' (Turbo and supercharged) units are really troublesome, a quick google reveals all, SEATS seem to have loads of issues.
So, jury is out, chain better than a belt, not really sure..
Hope what ever is fitted to our 1.5 TSI T-Roc when we finally get it has been fully sorted and will be trouble free.