I am currently using an iphone6 and want a bigger screen. Cost is abount the same. Whih wa is best?Dave Doll,
dolldave@embarqmail.com
p3pro since 2015

Sounds like your an "Apple" guy, and that is ok. Look at DJI's recommended list of supported devices and you'll see your choices there. I-pad air or mini may strike your interest, but yes they will be a little pricey as you already know.
You are probably not interested, by I use a Nvidia Sheild, which a lot of us android users do ,and it works extremely well for me and you can purchase these for under $200 brand new.

Tablet definitely, I have been using a nVidia Shield w/ 8" screen since May 2015.  It has a HDMI out port that I use to mirror my flight screen to a larger LED display so that others may watch in real time.