Built quality is as good as of 1.8. If you are happy with 1.8 then 1.6 will surely impress you. It is powered by Dual VVTi which is 12% more fuel efficient then previous VVTi and it is also a smaller engine i.e 1.6 so fuel average will surely impress you !
I have heard some members complaining about Sunroof but I am sure that was one odd case, Toyota must have rectified the issue and you can be more careful while receiving your Car.
Auto trims also comes with the Eco meter and Eco zone which monitors your fuel average in real time so they can further improve your driving habits and on long routes , cruise control will come handy to improve your mileage further.
Hope it helps