I'd avoid the Karma, it's had some SERIOUS issues (As in dropping out of the sky issues requiring a full recall).
GoPro knows action cams. They don't know drones, at least not yet, never get a first gen product like that IMHO.
Especially for a motorcyclist take a hard look at the DJI Mavic Pro. It's basically the same functionality as the base Phantom 4 but folds up into a tiny package that's easy to take on the motorcycle with you.
If you're heart is set on a Phantom, at this point I'd spend the extra money for the newer iterations, the Phantom 4 Pro or Advanced, not the base model.
Short example of the Mavic Pro and it's Active Track mode, the drone is totally in control of itself, I just told it to follow me while I rode around the parking lot, after riding my Valk to the area with the drone safely tucked away in a corner of my saddle bag:
https://www.youtube.com/watch?v=7sglxim7lFoLittle video montage I put together from the last *sadface* HotGlue's Gathering of the Fools, shot with my Mavic:
https://www.youtube.com/watch?v=TSA-cirG0r4