As has been mentioned, being a 2.4gig digital link there is very small chance of any issues.
However, under Australian MAAA regulations the transmitter must always be turned in before the remote device, and in turn the remote device must always be turned off before the transmitter.
Having been a registered MAAA pilot for near on 35 years it has become second nature.
My personal opinion on the MP however, as it is programmed to perform certain actions upon losing connection to the transmitter, like was mentioned above I do not want to risk that happening.
As for the iPad, I always turn it on first and it boots up while everything else is firing up. Then I fire up DJI GO and away we go!