Ill answer this with the limited knowledge i posses since I havent had the chance to try out any of them (Ill also include how Id set them up.
Fx Panthera 600mm .30cal: for the area I live in and the purpose I have for airguns, 600mm gives you agreat deal of precission while maintaining the rifle on a manageable length, shooting .30 cal slugs would allow me to reach out to further distances while maintaining the energy I need to take down the type of game Im after effectively, before you ask, yes it does have a low shot count (id rather keep the rail), and to solve that id have a couple spare 300cc bottle in my gear bag. As for the set up, accutac bipod, Vortex Razor HD Gen III 6-36X56 FFp scope, shooting 60gr Javelin slugs at about 960-980fps.
Fx Impact M3 .22cal: needles to talk about why Im going with the impact here, Backbone top rail, saber tactical arca rail, 700cc bottle, and the 800mm tensioned barrel wit a stx superior heavy liner, shooting 40gr slugs at 980-990fps, with an atlas bipod and the same optic as in the panthera, (and all the power block upgrades) basically a heavy slug set up, now the reason it is in second place for me is that with all the mods and accesories it gets incredibly heavy and almost annoying to carry if you are hunting on foot.
Personally I value precission over almost everything, and form what ive been able to see on youtube and social media, fx has that side of things pretty much dialed in.