I've had a T3i, G6, GH4 and now the GH5 in the dslr realm. All I can say is that they are some of the best cams for filming critters long range you can get at any price!
Lately I've been using a 15mm f/1.7 for wide angle landscape and hero shots. A 42.5mm f/1.7 for closer up action and a 100-300mm for filming critters when I'm hunting. When I'm just filming I carry a vintage nikkor 600mm on a giant tripod and fluid head that weights over 20 lbs. My total pack weight when I'm just filming with all my crap is over 50 lbs when carrying that pig.
Image quality is nothing short of amazing. With all that said, it's super hard to film heat of the moment action with a dslr type camera. The GH4 has super crappy auto focus in video mode (great in stills mode) and you have to have it on a very good tripod for the long range stuff.
If I didn't have the giant hand-me-down 600mm lens from my dad, I would be very tempted to just use an HC-X1 pro camcorder with 4K-60p, etc.... then use your PhoneCam on your spotting scope for the long range stuff.
6 of one half dozen of the other. It all depends on what you like to do.
If you're in the SLC area, I can show you my setup and how it all works.