Yes, for now, it is best to use the 5.1 analog output of your player if it's HD DVD or Blu Ray.
So if it's not, then....it's not the best route.
Unless your player has a DAC circuit superior to your receiver's. Or maybe some unique surround enhancing digital feature you prefer over anything your receiver offers.
Your player is DVD-audio and SACD capable - a universal player. So while its 5.1 analog output may not be the best, you have no choice but to use them to enjoy DVD-Auidio and SACD. I have yet to see a receiver with outboard SACD and DVD-A decorders.
You really shouldn't have a problem choosing. Because you can have both analog and digital connections to your receiver. And just switch to either whichever appeals to you. But you have to switch the receiver input to analog when listening to DVD-A and SACD,