[jjrh]

More detailed comments below, but in short: - lower power consumption (that you can control) - different environmental tolerances - peripherals with hardware support

Looks like this has a integrated Li-Po charger which should mean you can have a UPS like battery backup.

Folks may use this as a development platform that eventually gets a custom PCB made for the end product. ( it's open hardware so it has all the schematics https://content.arduino.cc/assets/Arduino-PortentaH7-schemat... )

It's really just different features for different needs.