Optical and coax will get you surround (Dolby Digital and DTS and multichannel PCM) but for the formats on Blu-ray such as Dolby True HD and DTS Master audio and now with Dolby Atmos and DTS-X these will only pass over HDMI. So if you receiver has it HDMI is best. Even if a receiver doesn’t support all the formats it saves a cable for now and will be ready when upgraded. Optical is still left there for older support but we’ve seen newer players leave it off and AppleTV and Roku models and other devices are HDMI only now.