I don't have any first hand experience of that controller personally, but have used their MIDIMATE amongst others.
Reading the Xchange manual on line it looks like it can be set to a single MIDI Channel and then will send Program Changes with the UP/DOWN buttons.
So the easiest way to do it would be to have both Factors set to receive MIDI on the same MIDI Channel and it would work as you describe.
The more elegant way would be to use the MIDI MAP function on the first Factor connected to the Xchange ….this would be more complicated to set up…but potentially be more flexible ….may not be needed though if you can live with the single MIDI channel set up.
