>>106993690
>and if they actually use separate amplification for both positive and negative channels you do get 4x the power, but end up with 2x the noise and 2x the output impedance
That's not true. It CAN be true, but some manufacturers limit the power output on the balanced output to match the unbalanced output's power.

My amp for example does 1.3W @ 32ohm on both unbalanced 6.35mm and the balanced 4-pin XLR outputs. Both outputs also have < 0.1 ohms output impedance.

The difference is only in the channel crosstalk where the 6.35mm output is -88dB @ 1khz. The 4-pin XLR output is - 98dB @ 1khz.