Theres a lot of mixed logic about this but on the US sites where the ca flys were readily available the owners mostly say the response is better and the torque of the turbo does the rest.
Also never seen a second hand ca18det lightweight fly for sale, maybe missed some maybe not.
Dumping the clutch at the start line after a quicker revving engine due to lighter fly would be tempting.
Even V8 supertaxis have ridiculous lightweight flywheels sub 3kg and those things are tanks with probably the same amount of torque as a worked CA18det yet your car is only 65-70% of their weight.