Carwow got a chance to compared the new AMG A45 S with the old AMG A45 and the first thing that stands out is that the old one sounds much better because of the new EU regulations.
As part of the review they compare the two cars in areas like 0-60 times and a rolling race. The old car reached 0-60 in 4.8 seconds while the new car did it in 3.9 seconds. They also timed an Audi RS3 and it did it in 4.2 seconds.
It's also pretty noticeable how much the interior has improved in the new car compared to the old one.