The M3 is a genuinely sporty decent car with power to back up its weight and luxury and keep it in the sporting section. BMW sports are not sporty enough to be fun and compromise on the SE, they are rubbish.
The difference between the two are night and day.
Do you have to bang this drum every time the word "BMW M-Sport" is mentioned? It's interesting you think this when every magazine article review has said that M-Sport BMW's are generally excellent cars?
What experience do you have with "M-Sport/Sport" BMW's?