Maybe the AC clicking is more noticeable because the Mk3 engine is so quiet 
. Back in the 1920's Rolls Royce told customers the reason they could hear the dashboard clock ticking was because the engine was so quiet - they used it as a tongue in cheek marketing ploy.
The clicking is solved on the Mk4 which uses an electric inverter AC compressor , independent of the engine. And perhaps inspired by Rolls Royce the Mk 4 drivers manual actually warns that you can sometimes hear background systems running which are normal but would be hidden by engine noise in a 'conventional' car. (You can sometimes faintly hear fans running etc.)
Yep, that's why sound proofing in HEVs, PHEVs and BEVs is generally more accurate than standard cars.
ABS/ESP systems perform a self test at every startup: since this test is noisy and some customers complained about it, vehicles do it when the car reaches 10-15km/h so it's hidden by engine and rolling noises.
my compressor clicks every few seconds more noticeable at idle.
I thought it was a problem at first , especially compared to my old Golf
European cars, apart from low cost and citycars, generally use variable displacement compressors, while japanese and american cars use scroll type compressors with fixed displacement cheaper and more reliable.
Variable displacement compressors are smoother when working in manual trasmission cars, most common in Europe: in low gears, you can feel a bump like a misfire when the fixed capacity jazz compressor engages or disengages, and this happens frequently because the A/C system must stop the compressor when it gives more cooling power than requested. Variable displacement compressors instead adapt the cooling power modifyng the displacement, so no clicks and no bumps. In automatic transmissions like CVTs or torque converters, there's never bumps even with fixed capacity compressors because the trasmission filters these knocks, so american and japanese brands (building a high percent of automatic cars) use more efficient scroll compressors.
