1. The interior if the E90, while Comparatively bland, is a lot more solid. There are better materials, there is less flex to a lot of the surfaces, and generally has the same or better quality look to it.
2. Hydralic or electric-assisted steering? You decide. But, I believe the jury has already ruled that hydraulic-assisted steering as the way to go.
3. Looks. While the new generation is lighter, the older generation just looks sleeker.
4. If I'm not mistaken and please correct me if I'm wrong in this, but I understand that they have replaced some of the suspension parts, that used to be aluminum, into steel?