Samsung with AB Mobile. If you want to be able to plot trajectories for more advanced things like urban prone shooting, don't bother with calculators that don't have an input for horizontal scope offset or ammunition zero offsets.
Just switched from an iPhone. Android is far less buggy, you can set the web browser to automatically go to desktop sites instead of the mobile one, you have a grace period to return apps and get a refund if they suck, there are more apps and better ones, the apps offered on both often come out on Android sooner (as do their updates ), getting photos off and putting music on is as simple as reading/writing to a flash key. It's painful putting things on the iPhone and getting photos off if you're not using a Mac. More bluetooth devices work with Android because Apple requires manufacturers to put a chip in their device in order to talk to the iPhone (why the bluetooth 4500 Kestrel didn't work with the iPhone). Also, the cable is a regular micro USB, and not a proprietary cable that cost $20 and breaks or the phone refuses to connect to every other month. Apple also puts that chip in the cables so inexpensive copies can'be made. On my iPhone 4S (before they added that) I bought cables from the Dollar store because they outlasted the $20 Apple ones.