Diesel vs. Gas Mercedes

I have the diesel fever. I want to try one. My question is how much better are they than the gas engines. I ran into a lady going into the grocery store the other day. I asked her how she liked the car. Her fist reply was it has a new engine. I thought diesels were supposed to last several hundred thousand miles!! Do you feel they are more expensive to maintain as a daily driver than the gas models? Any feed back would be appreciated.