Basically It's pretty much the same as C230K, but less horses and looks different - otherwise same car (especially inside) but costs a bit more
So if you are thinking of buying one and don't really need 4 doors, get C230, same or more features, same build quality, safety and reliability, and more horses for a couple of grand less...
If I've gotten my money back, I would probably buy C240 ONLY because it has 4 doors, less horses doesn't bother me much
Otherwise - I love my C230K. Great Investment 
If I've gotten my money back, I would probably buy C240 ONLY because it has 4 doors, less horses doesn't bother me much