The thing I found using both a Roland an later a Korg module is that you need many of the knobs and buttons nearby. The modules were more "table-top" than rack mount, but they were still somewhat bulky. They needed to be placed on top of or very near the controller keyboard and certainly did not work as seemlessly as an integrated unit.

I still support the idea of a module and would probably try another, but integrated arrangers seem to be way ahead of modules.