I have owned 3 300SE models. They have all been very reliable, and I am very pleased with the performance.
Maybe it's my luck, but in two of the models I've owned I have had to replace the water pump which was quite expensive.
My dad has owned a 420SEL and was very pleased with it. He owns a 500SE now. If I had more money I would go for a bigger engine, but fuel prices in the UK are stupid, so I will stick with the 300.
Whatever model you choose, you won't pe dissapointed!
---My Previous MBs---
87 300SE (Sold) - Black, Cream Leather
89 300SE (Sold and missed) - Black, Cream Leather
87 420SEL (Died!) - Bronze, Black Leather
---Father's Previous MB's---
2004 S320 CDi - Black, Cream Leather, 18" AMGs
2001 CL500 (Stolen!) - Black, Cream Leather
1999 E55 AMG - Black, Black Leather
1994 500SE - Black, Cream Leather
1990 300SE - Midnight Blue, Cream Leather
1986 420SEL - Diamond Blue, Cream Leather