Audio can be decoded in the player or in the receiver, and the default will usually be in the receiver. So it can make a difference, but not so much as video IMO. The decoding is different for video and is normally always handled on the player side. The Oppos are geared toward that sort of processing since that's their priority as compared to the Playstations, and they tend to do it better. Even the first generation Oppos were video powerhouses. I owned two or three of their earliest models (DVD) and they were all solid.
When you start talking about the analog audio of say the 105, there is a definite difference over the PS4. There is a noticeable difference between HDMI and analog even on the 105.