Experiences with Smart CDI - 45 PS & 54 PS; ECU

Hello,

I am currently considering expanding my diesel fleet with a Smart, in addition to my existing Audi A3 BKD and Lupo AMF.

I've always liked the 451 Smart.

Do you have any experience with the engine and can you tell me about the differences between the two versions (Euro 4 and 5) and their lifespans? Where are the weaknesses?

Who owns the ECU?
Do you think they are going to flash it with OBD?

Thank you.
Johannes