I have owned both [more than once].
The units with the blue circuit boards were made in the USA and were the older units.
The reddish circuit board units are the newer units and are made in Taiwan and are much less reliable.
The newer units have a different balance control and volume control than the older units.
The reddish circuit board units also have a issue with the balance control operation and the volume control operation:
On the newer units you have to turn the volume control much higher in active mode to achieve the same volume levels as the older units, because the balance controls are padded down with resistors when the control is turned "straight up" at the 12:00 o'clock position.
This supposedly was to make the active and passive modes nearer to the same volume level when flipping the active/passive switch on the front of the unit, but it hurts the gain, and transparency of the active mode, IMHO.
On the older units, playing your left and right loudspeakers, the sound is loudest from BOTH speakers when the balance control is turned "straight up" at 12:00 o'clock.
On the newer units the sound is loudest when the volume control is turned all the way to the left [left speaker] or all the way to the right [right speaker]. The sound level to both speakers is reduced when the balance is turned straight up to 12:00 o'clock.
The newer units also had issues with the remote control not controlling the volume and balance knobs correctly...They would overshoot or sometimes not move at all with the remote!
Passive mode remains about the same.
If anyone else has had similar experiences with these units, please share it with us.
The blue circuit board units are better, IMHO.