I see what you are saying, Don.
When I worked the music stores as a store employee, I had to learn the OS of every arranger brand we carried, at that time it was Roland and Yamaha. The store down the street from us sold Technics.
The last Roland arranger I worked on in the store (besides the G-70 I babysitted for a friend a few years later, was the G-800, and I remember at the time it was about the same as Yamaha regarding difficulty, and it was a riot going from one brand to the other due to the differences.
That's why I wouldn't use two arrangers, unless they are both of the same brand.
Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.