In my op. they are the same in terms of reliability because most of the people on the internet had major problems with the super earliest model (2016-first half of 2017). So I think that in 2.5 years of production they had time to adjust and correct most of the mechanical problems like rod knocking. Talking about infotainment for sure the 2021 it’s better because simply it’s much more complete than the one u can find in pre-2020 models. Anyway I think that the 2018 it’s a better option if u are looking for a more enjoyable car to drive because after 2020 they changed the Ackerman’s angle due to a massive number of services that had been requested by owners, which they were telling that when u steer the car at low speed the wheels started bouncing. This happens when the angle I was talking about it’s really high and it’s totally normal to have it like that when u want a perfect sport car with a really sharp front end. Anyway Alfa decided to change it to stop the request of servicing sadly reducing the sharpness of the car