My opinion is not worth much, but I think the 1.6 can be inspected the same as other vehicles, look for gear/engine behavior that sounds wrong - then it is probably wrong.
The difference, I think, is possible electric problems, airbag issues, and that any maintenance should have been conducted by real alfa mechanics. It is worth connecting a ELM/OBD cable to read errors (after doing test drive). Some errors may not show on the dash (sometimes the airbag/engine warning lights are conveniently not working).
Belts changed every few years. Seems to me the diesel is much stronger than the petrol but do check general discussion forum for the sticky thread on recommended garages.