I use my 7 inch connected tablet with the navionics app in a water proof bag so I can use my depth finder for sonar.
I still have the chip in my finder since I bought it before the tablet for back up if the tablet goes dead. I also have the app on my smart phone as I was using it before the tablet. So I have tried it all except running two finders one for map and one for sonar which I have seen on friends boats. It all boils down to preference IMO do what works for you.
A word of advice, I find it much easier to plan routes to different spots while sitting at home with either the App or the Chip in my PC.
"Ipsa scientia potestas est"-Knowledge in itself is power - Sir Francis Bacon
"Beware the lolipop of mediocrity, one lick and you could suck forever" - unknown author