I guess I'll try the Rapco device.
I use the Live Control knobs primarily to adjust mic reverb and vocal harmony levels. I'll try experimenting with other settings using the assign button or registrations to call up different assignments.
My approach to the senior shows I do is to keep things simple to minimize setup and takedown, and so I can give maximum attention to the audience. I think the PSRs have great mixers whose mic settings can be tailored for each song via registration memory. For me, that's the way to go. But I much prefer physical knobs to sub menus on a touchscreen, so I'll be excited to try the Rapco gizmo