The World Axis, because it was actually designed with intent to give us things that were worth playing in and which were motivated by classic tropes and myths, not just random pseudo-systematic BS that only exists to fill grid boxes and create a fundamentally modern and scientific worldview rather than a properly medieval or even renaissance one.
Half the "evil" planes of the Great Wheel are essentially indistinguishable, and so are several of the "good" ones. The elemental, paraelemental, and quasielemental planes are utterly superfluous 99% of the time, and the 1% that actually matters can easily be replaced with something better. I doubt even half of Great Wheel fans can explain what the Ethereal Plane is even doing. Etc.
Meanwhile, the World Axis has just five planes, all of them worth visiting (plus one scary bad un-place), all of them interesting and vibrant and mythically resonant. Mortal plane, Astral Sea (which contains both heavens and the Hells), Elemental Chaos (which contains the Abyss), Feywild (fairyland of magic and enchantment), Shadowfell (plane of death, undeath, and darkness), Far Realm (un-place of madness, corruption, and the unmaking of existence.) Comprehensive, effective, parsimonious, and significantly more like how the actual cosmology of Antiquity, the Medieval Period, and even parts of the Renaissance would view things.
