Neither op-amps nor discrete circuitry are universally better.  It all depends on the application.

For high-gain circuits, discrete circuitry is better because it has lower-noise.  Also, discrete transistors are commonly used for high drive-current applications, like amplifiers, whereas op-amps can't emit as much drive-current.

For line-level circuits, op-amps are better because they are more consistent.  Specifically, they have more precise matching between channels, especially with regards to temperature fluctations that occur when the device is powered.

Best,

Elias