Mine is the smaller screen and I find it fine. Depends how you use it really.
For pure navigation I'd use the single screen on chart, for pure "bottom searches" I'd be on sonar only and for pootling around saying "ooh look what we're going over" I have it on split screen. (My two young boys love that one). I also have it set so that sonar and down vision share the sonar half of the display so there can actually be 3 things on display. All work well for me.
There's weather out there - must be time to RIB!
(Or dive, or ref rugby, or.......)