Hi
Yes I have done both
My last boat had two 5" lowrance units side by side and worked great, it gave me a good set up and the knowledge that I would not lose both at the same time through breakdown.
I fitted these instead of a single 8" combi unit, as those had very small usable screen size when other navigational info took up some of the available space.
Alfresco however has a single 10" Lowrance combi unit
This has a big enough screen to make it usable when split screened. Also the navigation info can overlay the chart so it does not reduce the chart visable.
It is simple to adjust screen sizes to adapt which is the larger screen.
Another good feature is the recording facility, I use this a lot when looking at new marks/wrecks.
On the PC at home I can pick off features and get the Lat/Longs, [usually when Coronation Street is on downstairs ]
When I finished the boat, budget would only allow for one set, so I left room for a second to be added later. 5 years [and 700 engine hrs ] on and I have not added a second set yet.
Enough said
I have found that a trip to the boat show is the best way, get one of the experts to show you through the features on the various sets , then see what show deal you can get to fit your budget.
Charlie