The 1.8 TSI obviously is not as powerful as the 2.0 TSI and from the factory is rated at 170 horsepower versus 210 horsepower for the 2.0 version (horsepower varies based on the VW model and transmission but generally it is roughly a 40 crank horsepower difference). The 1.8 TSI is a great value especially considering output rises from 162 wheel horsepower (meaning the motor is a bit underrated to begin with) on 91 octane to 210 wheel horsepower essentially matching at the wheels what the bigger 2.0 TSI motor is rated at the crank with just a tune.
On 93 octane tune only output rises to 218 wheel horsepower so 8 more than on 91. The horsepower gain has a dramatic impact on acceleration as the video below shows and is worth every penny of the $599.00 APR is asking.
The 1.8 TSI features the same EA888 architecture as its 2.0 liter sibling meaning on paper some parts should transfer over and it will not give up too much versus its big brother especially once turbo upgrades come into play. One building the internals either the 1.8 or 2.0 should have very similar capability.
The more boost the merrier, right?