When considering a two channel DVR video systems, an mDVR system is a better setup comparing to a two-camera dashcam. Dashcams are fitted to the windscreen so they need to be refitted if the windscreen is replaced, they are more obvious to the driver and they can be more easily damaged or vandalised.
The mDVR has a built-in accelerometer to monitor harsh braking and has multiple I/O making it easy to connect a fuel monitoring device to alert against fuel theft or other functionality as required. Although the requirement is for a managed service, it may be of interest that the mDVR provides live view if required. It is available with a hard drive or a twin SD card.
The mDVR has up to 4 channels (x5 channels for HDD) so can easily have additional cameras added on the HGVs for FORS Silver compliance, i.e. nearside and rear. It can be fitted with a monitor for the driver to view the cameras when turning or reversing. to supply side sensors for detection of cyclist and pedestrians.