BMW and Audi both are top luxury cars and have their own pros and cons. There is no single comparison by the top quality assessing agencies that can be quoted in this regard to get convinced about the superiority of one over the other. Still, there are parameters based on which some subtle distinctions can be made.
If we see the reliability factor then BMW scores a bit ahead of Audi in some of the assessments by a few agencies. At the same time, if we look at an overall perspective in the luxury class of cars then, mostly based on the assessment of the agency known as US News and World Report, Audi fares slightly above the BMW.
On the warranty front, they provide similar propositions and nothing much there to compare. Both are highly customer friendly. However, on the safety front, more Audi vehicles qualified as compared to BMW.
Another interesting thing is that these cars have various versions year to year wise and it is possible that in one version BMW scores while in another version Audi scores. So, we have to keep that aspect also in consideration while comparing them apple to apple.
If you are interested to know in more details about these subtle variations and differences, I will suggest you go for more information at -
Knowledge is power.