What is the purpose of /sys/block/sd?/device/rescan?
Solution 1:
Strictly speaking they are not equivalent but they may achieve the same outcome.
The first command requests the system rescan the specified device for changed device parameters.
The second command deletes the specified device and rescans the SCSI subsystem for new devices and reads their parameters. It's possible then, that additional changes not related to the specific device may occur.