Having recently driven an 85 and 86 S-class Mercedes, a 420 and 560 sel I can truly say that the Caprice is more comfortable. It is definitely a simpler car, which may be part of its charm, but the seats are much more plush, armrest better positioned, the car rides smoother and is easier to control. I might add the blind spots are less as well. The seats in the MB are rather hard and unsupportive. The ride isn't as confident and noticably smooth either. The MB feels more solidly constructed, but just not as enjoyable to drive.
The ride on this car is unreal, it's so smooth it doesn't even feel like a regular spring and shock suspension, it feels like it has air ride or something. It's hard to believe it's built on a platform designed 30 years ago and can ride that well. It can handle surprisingly well also. With a rear sway bar and a larger front one I'm sure it'd be better still.
Performance is good, but with a 350 it'd be perfect. The 305, which I believe was only produced by GM to meet CAFE emissions standards struggles in overdrive, especially on grades, however it does remarkably well with fuel economy.
Mine has a very annoying knock under load or ascending a hill, it could be bad fuel or detonation, I've yet to find the cause. The motor has had some shoddy repairs done to it in the past which may be one cause. At any rate I'd prefer to simply put in a mild 350, keeping the fuel mileage, but increasing performance. A car like this deserves a motor just as good. No wonder Chevrolet sold millions in the late 70's. A real winner of a car.
Very reliable and easy to service as well. It's really much like an improved 1960's car, being built the same way, body on frame, V8, RWD, etc, but with refinements and engineering improvements that were added and learned over the years. Much more of an effort was made to prevent rust than on GM cars built before the Caprice.
I would never trade my Caprice or any b-body for it's competitors of the same era. I can only imagine what a full-size Cadillac must be like being a close relative!