Thanks guys. Both cars are at dealerships and both come with limited warranty (30 day 1000 mile) AND I am covered by NY's Lemon Law. Both dealers have good reputation. Many people here have purchased from both dealers and almost everyone in my company that has a mercedes (17 or 18 people) use this indy shop and recommend them.
I will now just have to compare the performance differences and review the records to see what has been done. I will have the indy shop review the 420 and let me know what they think.
I have a 190e that gave me a ton of trouble. I spent more on the repairs for that car than I paid for the car. So, I am familiar with the big expenses that a used mercedes (or any car) can cause.