I went with just short springs (Eibach).
I love what it did to my car. I hate the standard height of recent Bimmers. Couldn't live with it.
My ride quality is just fine. However reality check means that you can be vulnerable to snow accumulations. I rolled over a block of ice and it cost 521$ to fix the under covers. Unsure if that would be the same with regular height. C&D also had this issue on their long term M3 to fix a similar incident.
Would I do it again?
2007 E90 AW 323i Step | Lowered 1.25"/1" | BMW Performance Exhaust | Debadged | Scangauge II | Style 162 18" & 161 17" wheels & rear 15mm spacers