I did test drive both cars C43 and S4 and I am confused which one to go for. I understand the engine and interior comparison. But I am not able to judge which one is good for long drive (say around 8 hours with breaks (not everyday, just once in 3 months)).
I as I can not test drive a car for 1 hour, I am not able to figure out. So the question basically boils down to which car has more comfort so that at the end of drive driver will not feel tired. For example Lexus is known for that comfort. But for S4 vs C43 which one will have better and comfortable steering wheel handling, comfortable room for driver and overall comfortable ride? Please help.

 

You are in the wrong forum. This forum is for the next generation C-Class. You might have more luck posting in the correct forum for the current C43.

https://mbworld.org/forums/c450-c43-amg-216/

As a long time Audi S and RS owner and current owner of a 2019 C63S, I can perhaps shed a bit of light on this. Comfort is to a large degree subjective. Perhaps if comfort is one of your top priorities, then a car with a sport tuned suspension is not exactly the right choice. To further complicate the issue, these cars can be configured in different ways that affect the comfort level. For example the C43 comes standard with adaptive suspension, but it also comes with run flat tires from the factory which are pretty much universally hated and blamed for terrible ride quality, however, one can always replace them with a different set of tires later on. Then you have two choices for the seats. The standard seats are supposed to be more comfortable, but you can upgrade them to the AMG Performance Seats, which are proper sport seats, but some people find them uncomfortable. I personally love them in my C63S and I've done single day trips up to 12 hours in them. The S4 on the other hand comes standard with a fixed suspension and optionally can be configured with the adaptive sport suspension. It comes with regular summer performance tires, so no run flat crap and there is only one choice of seats. Wheel size also makes a difference. Both of these cars can be had with 18" or optional 19" wheels and tires. 18" will be more comfortable due to the additional sidewall height than 19". Seat comfort is to a high degree affected by your own shape and fitness level. You'll find lots of opinions on seat comfort. For some they are uncomfortable, but others find them super comfortable. Only you can decide which seats feel more comfortable to you.

In general, though, overall Audis are softer than their respective AMG competitors. They are overall more comfortable daily drivers, but on the other hand not as engaging or exciting as an AMG. However, that's generally speaking. Personally, I find my 2019 C63S on 19f/20r wheels drives more comfortable in Comfort mode than my previous 2013 Audi RS5 with fixed suspension and is more dynamic and much better handling in Sport+ than my RS5 was, and I also much prefer it over the current generation RS5. So it's all relative. One thing to understand is that with an adaptive suspension it's not just that you can choose between different modes (Comfort, Sport and Sport+ in case of the C43), but also that the damping is continuously adjusted based on road conditions and how you drive. So overall an adaptive suspension is more comfortable even if it has slightly stiffer springs, because of the active damping. A fixed suspension such as the one that comes standard with the S4 is a compromise between comfort and handling.