Mainstream + Mass market cars are getting boring actually. I certainly do not want a midsize sedan anymore, I want something different these days. The rest is so boring! A BMW 3er or Audi A4 or any other Lexus IS and C-class is so 'yesterday' that is why I'd rather have a niche product from this segment like a 4er or Lexus coupe, I simply don't want a little (everybody has one) premium midsize sedan. That's me, the buyer they have to deal with. Hence coupe's, crossovers, 4 door coupes, Sport-back's etc. existence...
Just for interest sake, try this out.
What really, really, really, REALLY set these two apart from each other?