Why does the reliable BMW 6 Series only get three stars under your ratings system?

I am looking to upgrade from my BMW E46 330i to either a BMW 645i (E63 - 2004) or a BMW 325i coupe (E92 - 2007). You rate the 3 Series with five stars yet it has a lot wrong under "What's Bad" whereas you rate the 6 Series as only three stars but with virtually no "What's Bad". I find both very desirable and would potentially be happy with either. I have always found your Car Reviews and other advice exceptionally helpful, especially in helping to avoid potential pitfalls, but this time I am very confused as to which is more likely to be the less problematic (I appreciate no cars are faultless these days).

Asked on 9 November 2013 by AN, via email

Answered by Honest John
I'd better explain how these star ratings work. In the first instance, cars are rated as to how they work on test: how well they fulfil their design brief in comparison to other cars, how well they drive, how efficient they appear to be from the EC ratings, and what can be gleaned from a few hours driving on a car launch. But those star ratings can be later downgraded as faults are reported to us. 3 Series on UK roads outnumber 6-Series by at least fifty-to-one, so there are far fewer reports of 6 Series faults. So far we still think the E92 3-Series still rates five stars, particularly the 335i manual, despite the problem areas. We simply don’t rate the E63 6-Series as highly, either as a driver’s car or on the basis of reader reports.
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