The 600SL is certainly a modern-classic that not only exceeds in looks, but in performance too. The 6.0L V12 engine offers more than enough power, while the handling of the vehicle is superb. However, the greatest achievement of the 600SL is the ride quality. It is heavy enough to iron out most rough terrain. On the other hand, reliability is an issue, especially with the electrical components. The heat from the engine also does a number on certain plastic parts within the engine bay. The biggest challenges one will face with the 600SL is the wiring harnesses and insulation.
It's comfortable, torquey, fast, & reliable. If you're in the market. Be sure it has a service history, & repair records. The repairs aren't terribly expensive, especially if you know how to do some of the simple work yourself. If you're considering the 500sl or the 600sl, do yourself a favor, and buy the 600SL. You won't regret it. Seems to be more reliable long term as well. Harry's garage on YouTube (who owns many cars) chose this as his reliable, daily driver in Europe. This car is fast. And outperforms most cars on the road today, even modern sports cars! It's safe. The design of this car started with safety. I highly recommend it.
Here is what you should know: This is a 119,000 car new. When writing this review, that would be about $200,000 with inflation. That's a lot of money to just about anyone. The great thing about this car is that you can walk up to it expecting a car worth that amount of money. It's fast, it's smooth, it's comfortable, and it's safe. You pull up to a stop light and wonder if the engine is on or off because it is so smooth! As the light turns green, you test the engine with a little tap of the foot and off you go. The raw, naturally aspirated power takes you from 0-60 in what feels like no time at all. The suspension is smooth. The convertible top is ahead of its time. Mercedes Benz has always impressed me. Yes, you will spend some money if you bring this car into the dealer. It's a Mercedes Benz. If you know how to turn a wrench, and use air tools, you'll find this 600SL to be a pleasant surprise. I would expect approximately $400-1000 per year in maintenance & repairs. I can't think of a better bang for your buck on the market today (2017). I estimate that in 5 years time, these cars will fetch $20,000+ and in 10 years... somewhere in the $40,000s. It's timeless design, matched with a well designed v12 engine... low production numbers, etc... I'm excited to see the value of these automotibles rise in value.