Not all coaxial rotors are slower. A coaxial design solves the retreating blade problem at high speed.
The Russian engines are historically sub-par.
The coaxial design increases payload for the same engine power and eliminates the need for a tail rotor. They are a bit easier to fly in close quarters and quieter.
They are a good fit for naval operations.
The trade off is they tend to be slower and taller and have a pretty complex transmission.
To me, they look like a large target.
But then, so does any helicopter.
Complex and Russian is a recipe for disaster.
Not all coaxial rotors are slower. A coaxial design solves the retreating blade problem at high speed.
