I would say the E55. I absolutely HATE the look of the older C classes, very cheap looking inside and out, even the AMG.
E class on the other hand was nice. My dad had an 02 or 03 E320 and it was a quality car. (he now has a SL550 and my mom has the E class ('12 E550)... and the E has kept it's quality over the years. I would definitely go for the E!