HDMI is better than optical as it can carry higher quality audio formats.

Optical is limited to Dolby Digital/DTS. See https://support.sonos.com/en-gb/article/supported-home-theater-audio-formats

Also HDMI-CEC can be enabled so the soundbar and television can talk to each other, whereas optical is one way communication only.

The Sonos Ray is an entry-level soundbar, therefore it is not capable of playing Dolby Digital Plus or Dolby Atmos etc. If those are important then the Ray is not a suitable product for you and you should consider either the Beam (Gen2) or Arc.

Having only an optical connection is not necessarily on its own a bad thing. Many people still enjoy the Playbar for their television viewing and it only has an optical connection.