My thoughts on this would be to have my largest easiest to read screen at the console and a good DI unit at the console with a screen large enough for DI and mapping. I would prefer the units networked so they could share waypoints. This would be what I would like to try. At the present I have a 998 on the bow and a 798 at the console networked together. With the smaller screen on the 798, I often am switching views by my short cut buttons from the map view to the DI/2d and to the SI. I would think an 1199 at the console and 999 on the bow would work really well. I usually don't use the SI much when I am on the bow, but use it all time when at the console.
Of course a guy could just get a couple 1199s and not worry about what is better where