The main difference between the SCD953/26 and SCD923/26 lies in the additional functionality. Both offer similar functions such as night vision and digital zoom, but the SCD953/26 includes a full HD camera, 15 soothing sounds and the Baby Monitor+ app for monitoring via smartphone.

The SCD953/26 appears to be newer and more comprehensive than the SCD923/26, due to the additional features mentioned. Nevertheless, both models offer a secure connection and good image quality.

In terms of operation, both models are designed to provide a stable and secure connection, but the SCD953/26 could be considered better due to its additional functionality.