I upgraded to a 3 from a 1 and it is a better car. The main improvement is that it is much quieter especially above 30 mph or so. Steering wheel controls for phone, radio and music are great too as is Bluetooth that just works. I think the electronic driver assistance is a benefit too but some people don't agree.
The engine is not quite as silky as the GD1 and the car is also a bit less nippy especially at lower revs. However, it is noticeably more economical.
Handling and suspension is even better than the GD1. It is very stable and predictable.
Vision through the corners of the windscreen is better but there is still a blind spot to beware of.