Compromise..... And technical choices....That's all. Depending the result wanted : Speed, high and hot, maniability, Mountain flight, noise, payload etc.... The II Intelligent Ingeener make different choice to reach what the customer/market want...No more no less... And sometime you fly a very quiet helicopter without any defense on the pedal in high mountain... or very speedy helicopter but with a poor payload...
The perfect helicopter is only perfect for his customer and his use...