I realize that this is a loaded question with many opinions.  After flying the Phantom 2 for a couple of years I have decided that my new drone will be a DJI Phantom 4 Pro.  I have flown the P4P+ and was impressed.  Much has been said about the Ipad Mini 4 as being the best tablet to run the GO 4 app on.  The WIFI version of the Ipad Mini 4 is less expensive than the WIFI plus cellular version.  My understanding is that the WIFI only version does not have GPS and that the cellular version does.  Is it worth the extra cost to get GPS on the tablet?  What are the drawbacks of not having GPS on the tablet (Follow Me not work)?  I like the thought of having an Apple tablet versus the P4P+ because you can install the GS Pro on it and not on an Android device.  I have also read that many Android devices have had issues.

One more thought (question) if the Apple platform is the preferred development environment for the GO 4 app by DJI, why are the P4P+ and Crystal Sky devices using Android?

I look forward to your thoughts.

My 2 cents worth: I use an iPod  5th gen, wifi + cellular. I decided for the cellular version because it has GPS and because with a cheap SIM card from a local provider I can get data service -should I need it- even when WiFi is not available.  Also, I think that without GPS in the tablet one's location (= the RC location) would not show in the map in DJI GO 4, only the drone location.
Also, I think the Android platform was chosen because of the Open Source software it runs, while the Apple Platform is not available to third party hardware developers, I mean, they can't make third party tablets and run iOS.

Having a GPS enabled tablet allows two functions that can't operate otherwise.
1.  Follow-me flight
2.  Resetting the home point to the current location of the controller

That's all and neither function is particularly useful for most flyers.

Newb here.....P4A.......Read here where the IPad Air 2 was a good fit.   I already had one, but WIFI only.   I also have IPhone 5s with hotspot.   Turn the hotspot on, connect with my Ipad, and I have full coverage.  Still new enough to be spearminting, but seems to work very well.

Rvrrat14 Posted at 2017-8-16 14:23
Newb here.....P4A.......Read here where the IPad Air 2 was a good fit.   I already had one, but WIFI only.   I also have IPhone 5s with hotspot.   Turn the hotspot on, connect with my Ipad, and I have full coverage.  Still new enough to be spearminting, but seems to work very well.

Unless you want to use follow-me or reset home to controller's location, there's no need for any hotspotting.
Just use the wifi only ipad on its own and you'l have no issues.

As Labroides mentioned, the GPS mobile device is mainly used for Follow Me and reset the Home Point of RC location. Take it consider when you make the decision.