iPhone 6+
Looked at the iPad and iPad mini, but decided to go with the iPhone 6+ due to cockpit size. GPS position comes from a Bad Elf Pro (bluetooth) sensor. The cellphone GPS sensor will not update fast enough for aviation use.
I am using ForeFlight which gives me VFR and IFR charts, real time PIREP, METAR and TAF plus radar and satellite weather, terrain and obstacles, flight planning, weight & balance, logbook, etc. etc.
ForeFlight also runs on the home computer so I can do flight planning and transfer everything to the iPhone when I am ready to go out the door to the airport.