Hi Dave I have experience of both engines as we had the 1.2TSi in a Rapid Spaceback for nearly 3 years from 2015 and 28,600 miles which was quiet and reliable,used no oil between 2 services and averaged 45mpg mainly with wife driving it on her commute. In 2016 bought a Superb with the 148bhp 1.4TSi ACT engine both cars had the 6 speed manual gearbox which were nice to use. I did 16,000 miles in the Superb and averaged 50mpg and it was also quiet and used to oil. If I had to choose one it would be the 1.4TSi yet both engines are capable of delivering over 60mpg in the right conditions and a light right foot.

If it was me, i'd go with 1.4TSi; it's a brilliant little engine very refined (unless pushed) smooth and quite, yet the power and torque are fantastic for it's size and suits the Octy 3 really well.