Of all the published cosmologies, Eberron is my favorite. Because the outer planes are not simply representations of a particular alignment they are far more interesting thematically. For example, Dal Quor is a plane of dreams, Shavarath is a plane of war, etc. The existence of manifest zones, and the movement of planes making them coterminus during certain times lets the planes have influence in the material world in a way they don't with other systems.
In general though I don't think a particular cosmology is important, or even meant to be taken literally. I imagine that things like "the great wheel" or "the world tree" are just models philosophers and theologians have come up with to make sense of something mortals can't truly comprehend. Different sages in the same campaign setting should have different views about what the planes truly look like. The planes should be mysterious and not fully knowable, rather than something that is treated as a blueprint.
In general though I don't think a particular cosmology is important, or even meant to be taken literally. I imagine that things like "the great wheel" or "the world tree" are just models philosophers and theologians have come up with to make sense of something mortals can't truly comprehend. Different sages in the same campaign setting should have different views about what the planes truly look like. The planes should be mysterious and not fully knowable, rather than something that is treated as a blueprint.