Largely, you are correct. The ipad Navionics
app + maps dose the same job as the more expensive Fugawai + navionics at about an eighth of the cost!
However, the iPhone
version is different to the iPad
so you effectively have to buy it twice if you want it on two devices.
The "full" version provides not only for Fugawai, but the came map set will then be transferrable to a MFD or chart plotter. Also the Fugawai will allow for improved management of tracks and route
planning. Also, it permits AIS
Whilst I have the iPhone
app, the iPad app and the full Fugawai + Navionics like you, for 90% of my sailing, the iPad/Phone app works just fine.
But isn't half the fun, playing with and masterng the various things we buy that hardly ever get used!