Ok ive had both, the Nexus is a dam good tablet but its Android, which as you know does have issues, the Ipad is a good choice as its an apple device and rarely suffers issues, that said in regards to GPS, you only need it if you use something such as active track mode and want the dynamic home point to work, also GPS is used if you want to set home point to your current location, other than that i cant see any reason to have/need GPS on the device.
The RC does NOT have GPS built into it( a popular misconception).
Me personally I like the ability to be able to able to install any DJI app version so I would choose Android everytime, unless you want to mess about with Charlesand Itunes to rollback the app version on Apple.