I appreciate what you are trying to say, but we mustn't forget that there are some amazing V6 engines out there as well. Consider the Nissan GTR, a car that competes in all performance categories with supercars costing up to ten times its price.
Speaking of supercars, and speaking of Jaguar too, credit must be given there as well: http://en.wikipedia.org/wiki/Jaguar_XJ220
It isn't necessarily the engine layout that will make the next M3/M4 a great car (nor any BMW for that matter, though it doesn't hurt either), but I agree with you that the I6 tends to have a better exhaust note.
Originally Posted by Holander
B9 RS5 will get V6, Toyota Camry uses V6...but M3 will use I6, like first Jaguar E-type. I6 just sound hundred times better and rev to red line faster than V6, many not seems know how huge differend is between these layots, allways talking "six cylinder engines".