Not much help if you already have an iPhone (unless you are near an upgrade opportunity) but my preference is for Ipad tablet and Samsung (S4 now S5) phone. The IPad with Navionics is brilliant, go 3/4G but don't take out a contract just top-up a 3 sim as and when required, having had both large and mini IPads I prefer the mini. Good luck.
I understand some of that, are you suggesting I have both ipad and and iphone by samsung.
My i4 iphone is my own, not subject to contract, and I did not anticipate changing it, just trying to get to grips with the terminology so I can understand what does what and make a decision. It is an area I am not familiar with.