Boss,
I just traded a Motif in on a PA 80. For my 2 cents worth......an arranger can do pretty much all of what a workstation can do with the exception of deep editing capabilties and an arppegiator. The arranger on the other hand has the auto accmp. capabilities, that a workstation does not and easier to work with.
You can on a PA 80 send a click or beat out on a seperate track. There are 4 different ways you can send it out L&R out 1 out 2 or out 1&2.
If you liked the PA sounds, then I don't think you'll like the Motif sounds (other than the pianos). In my opinion the workstations (most all of them) are geared to the techno, trance, hip hop market, with both sounds and beats etc. The arrangers are aimed at a mellower sound.
Terry