With navionics app you pick the maps you want to download so you can get away with a normal ipad(non 3G,4g) and buy an aftermarket GPS reciever that will perform 100x better then the built in assisted GPS junk that comes on them, they connect via Bluetooth. Do a quick google search and you'll see what I mean. Of course the 3G,4g will open up many other doors in terms of Internet access on the fly, but depending on your needs u might want to look into the add on GPS unit and a basic ipad. Just an FYI.