@ salman_ksa
I have alot of respect for Merc, but u are going to loose this one mate, as BMW and Porsche are both Performance oriented. Merc tries but thats pretty much all it does. Sorry mate !!!
http://youtube.com/watch?v=TVD4GAPulRc
Look at this most powerful Brabus killed by a Porsche in a STRAIGHT Line, add some twisties and it wouldnt even be funny. So if you wana talk about merc , talk about its strong points, as in comfort and tech stuff. which merc is really good at.