I have just come from a BMW (albeit a Z4) to an ISC
A key point for all marques with road noise is tyre choice - the same with BMs, particularly the runflats are terrible over pot holes etc
I am waiting for my Bridgestones to wear down so that I replace them - probably with Goodyear F1 asyms
The biggest difference is the amount of noise on BMW forums about the many problems folks have with them and poor build quality for circa 1 in 5 new Z4s, the poor paint, rubbish dealers etc etc
I worry much less with a Lexus than a BMW