This has come up many times here and it seems to be equally divided,the Koni shocks are about twice the cost and get some good reviews and I know of
One Member that would gladly exchange his for the Bilsteins that he used on a previous RV,expensive is not necessarily better.
The Koni shock was not in production for Class C when I wanted new shocks but even now I would not opt to buy them.
I will recommend the Bilsteins they did not make the ride any harsher and stopped the porpoising and the ride is smoother and cornering has lot less body roll.
I have used Bilstein shocks on all my vehicles for many years and have been pleased with their performance.