What is the difference between the two?
The former has a sound decoder and speaker pre-installed, the latter has a standard DCC decoder pre-installed and won't make any noises aside from the motor and gearing.
There's also a third category called 'DCC Sound On Board' which has more options than the Sound Value series.
Bachmann uses 'dual mode' decoders that will run on both DC (analog) and DCC (digital) controlled layouts, but you need to apply about 5 volts in DC mode for the decoder to wake up and pass the voltage to the motor.
Welcome BobZ
If you look at the different diagrams on the Product Reference page you will see the differences.
The CV list are obvious.
Rich
Thanks for info.