The digital outputs (optical/coax) are for sending the DTS/AC-3 surround code from the DVD's to the surround decoder in your HT receiver.
If you are playing regular music CD's the analog outputs are what you are using, unless you are using a separate audio DAC (digital to analog converter) like the MSB Link DAC, (and others, etc), in which case you would also use the digital outputs..
As far as optical vs coax; most people prefer coax; however, if you really want to know what works best for you, then you should really try it both ways yourself. The cable used can have a large effect on results..
If you are playing regular music CD's the analog outputs are what you are using, unless you are using a separate audio DAC (digital to analog converter) like the MSB Link DAC, (and others, etc), in which case you would also use the digital outputs..
As far as optical vs coax; most people prefer coax; however, if you really want to know what works best for you, then you should really try it both ways yourself. The cable used can have a large effect on results..