I've owned 2 F10s and before buying the second, I borrowed an F06 demonstrator from the dealer for 3 days on an extended test drive, during which time I drove it over 400 miles. I am in the UK and tested the F06 as the European 640d model, which is the 3 litre 313hp N57 engine, the same one that I have now in my F10, which is badged as 535d (the US 535d has 258hp and is what we call the 530d in Europe).
The F06 is more or less an F10 mechanically but made to look sexier. In summary, I would say the F06 has in ts favour:
- Exclusivity (the flip side of it not selling so well I guess)
- Low down sporty driving position
However, against it, I found:
- Rock hard suspension
- Standard seats lack lumbar support
- Interior rattles, mainly from the front seats which are the same ones as the 6-series cabrio with the integrated seat belts
- Very long bonnet made it difficult to park in standard UK sized spaces (not an issue for you guys!)
- High depreciation makes it expensive to run
- Limited space in the rear, it is a 4 seater not 5 due to the transmission tunnel
Things that made very little difference between the F10 and the F06
- Driving experience
- Fuel economy
So for me the F10 was the right (if safer, more boring...) choice.