Mercedes used the straight 6 until 1997 in many different sizes: 2.6, 2.8, 3.0, and 3.2 liters with both single and dual overhead cams.
The V6 was used starting in the 1998 model year in the C, E, and S classes.
If you do a search you'll be able to read a lot of the opinions on the merits of both the inline and V6's.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".