Tiger, is your NSX an older N/A model or a new fancy pants hybrid?Along with the 4C, I currently own two other mid-engine sports cars (NSX and Cayman S), and track them as well. In the past, I've owned both rear-engine and front-engine sports cars.
Based on my own personal experience, the 4C behaves quite differently from front-engine sports cars. However, I wouldn't necessarily say that the 4C is more difficult to drive compared to other mid-engine sports cars I have owned/driven. Yes, imperfections on the road are more amplified in the 4C due to its narrow tires, lightness, and short wheelbase. Nevertheless, I don't think that it's unforgiving.
For example, I have had many situations where I would enter the corner too hot, and lift the throttle/trail brake in the middle of the turn. In those situations, it's relatively easy to predict when the rear is going to lose traction. And when it does, it's not as more difficult to correct it than with the NSX or the Cayman S. In fact, all my "spun outs" happened with my NSX where once I lost traction, it was game over. I wonder if the sensation of rawness of the 4C is giving the impression that it's a harder car to drive. It took me some time to get used to its sharpness - it's especially noticeable when you drive it back to back after the Cayman S - but once I got used to it, I found the 4C to be as forgiving as the Cayman S to drive fast.
One area I can pinpoint where I do have harder time with the 4C vs the NSX and the Cayman S is modulating the throttle input due to the turbo spool between 2K-4K rpm. However, this is more related to the inherent difference between NA cars and FI cars.
Just my 2 cents.
Both are very cool, goes without saying you have a nice collection there and thank you for the insight.