Qcomp

[x264]

does increasing the value of qcomp improve the video quality for animation?

[Selur]

Curve compression is ment to adjust the bitrate distribution between the two extremes a constant bitrate and a constant quantizer distribution.
Additionally a higher curve compression will lower the effect of the makro block tree rate control if it's activated.

0.0 => Constant Bitrate, 1.0 => Constant Quantizer, default value: 0.6. (personally I prefer 0.5, since I otherwise x264 sometimes doesn't hit the desired file size during 2pass encoding for me.

-> at the same output size: I doubt it
Better have a look at the adaptive quantization and the psychovisual settings of x264.