Individual vs. Identical Channels

Could anyone out here explain the differences between Individual and Identical MIDI Channels in the “Create New MIDI Device” dialog? The MIDI Devices manual doesn’t say very much as to the benefits of one vs. the other. But it does warn that “Once you set the attributes (identical/individual channels, snapshots) here, changes can only be applied with major effort like direct editing in XML”. This suggests that if you get it wrong, you’re in big trouble to either go through a lot of complex editing or delete the device and start all over again.