The Kompressor was a good way to soup up the four cylinder engine and keep the sales up.
I drove a 2001 SLK230K six speed before buying my C240 six speed. The power was great, everything felt great. What made up my mind was; I couldn't afford to go to the SLK320 to get the better V6 engine and the C240 was peppier than I expected, with the more updated high-tech engine.
If you want more information about the massive long term durability advantages of the high-tech V6, go to Featured Cars and read my post "M112 Engine Review". This will keep me from having to rewrite it here.
The V6 is an absolute engineering masterpiece. Additionally it has been out long enough now that we would have seen any acchilles heel if there were one. The four cylinder Kompressor is just not the level of engineering art that the V6 is. My bet on the C240 was because I feel that it will be longer lived. To have this same engine technology in an SLK, which I believe in general is a cheaper built car, would require about $10K more.
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in