An SD card is using contact pins to make the connection, which is susceptible to dirt and vibration. eMMC is soldered to the board so you no-longer need to worry about environmental and mechanical disturbances.

The eMMC has a known supply chain and is guaranteed for 1 million write cycles that are then wear leveled. The SD card could be coming from anywhere, or a counterfeit with who knows how many write cycles and wear leveling.

The CMs are built for industrial use and I've shipped a few products based on them, shipping thousands of units. They have had zero flash failures.