In most linestage/preamps with a balance control, the signal for each channel is going through two attenuators, one being the balance control and the other being the volume control which has two separate potentiometers to attenuate each channel. Having two separate volume controls eliminates one set of attenuators, but, it adds to difficulty in changing volume while maintaining proper channel balance. It is particularly hard to do remote control of volume this way.
In linestages that have relay switched resistors, the signal from each channel can be independently stepped up and down so that both volume change and channel balance will be achieved through the same stepped attenuator, thereby minimizing signal degradation. This also allows for easy remote control of both volume and balance.
To me, remote control of volume is an absolute must have feature. It is very hard to set the ideal volume level if you have to go back and forth between your chair and the equipment to listen to the result. It might be good exercise, but it makes for less than ideal listening.
