If you need to use features that require an Internet connection while flying (like live streaming video to YouTube), then you should use a cellular iPad model. Without cellular on the iPad, you could also connect the iPad to a hotspot on your mobile phone to share the Internet.
Only cellular iPad models contain a GPS receiver. That GPS receiver is active whether or not the cellular service has been activated. With GPS on the iPad, you'll be able to use the Follow Me flight mode and manually reset the home point to the iPad's current location mid-flight. If you need to use either of those features, then a cellular model is a must-have.