My guess would be that if you are actually wring the neck out of the car then you will notice a slight difference in performance but they are basically the same engine.
The early Elegance models all came with cloth seats as standard, Avantgarde came with half leather. My wife was very much an Elegance type person who liked the older styled wood finish with black dials, but we had an Avantgarde demonstrator for a week and those white dials with black trim grew on her.
If you are a performance type person that enjoys knowing when you have driven over a one penny piece, then don't forget the Avantgarde has a firm, sporty type suspension compared to the more executive ride of the Elegance![]()
The wheels are also of different styling, but to me it is the suspension issue that you might want to consider. One option that overcomes this is airmatic, but if your buying to a budget then this might not be available.
If your wife intends using the car then I would strongly recommend you see how she gets on with the opening and shutting of the tail-gate. If your the sole driver then disregard my last. The reasons I say this is because some members have mentioned just how heavy the tail-gate is and wished they had gone for the optional electric opening option.
Good luck with the quest
Regards
John
Slight clarification John. The E280CDI has basically the same V6 3L engine as the V6 E320CDI engine. The 2004 year E320CDIs referred to earlier in the thread are the straight 6 3.2L version (as in your car).