the m means motorsport
M6 Coupe
As of summer 2013 the official website lists the following BMW M car models: M3 Coup̩, M3 Convertible, M5 Sedan, X5 M, M6 Coup̩, M6 Gran Coup̩, M6 Convertible and X6 M.
it has the same style but m,s are known for more quality engines
The 2010 BMW M6 has 40 valves.
The 2007 BMW M6 has 40 valves.
The 2009 BMW M6 has 40 valves.
The 2006 BMW M6 has 40 valves.
The 2014 BMW M6 has a V8 engine.
The 2008 BMW M6 has a V10 engine.
The 2014 BMW M6 has 32 valves.
The 2013 BMW M6 has a V8 engine.
The 2006 BMW M6 has a V10 engine.