The Shira route is the only route that starts at a relatively high altitude and approaches Kilimanjaro from the west. Although it is a varied and beautiful route, its starting point at a high elevation means it is not as good for altitude acclimatization.
The route starts on the Shira Ridge and covers the entire Shira Plateau, which is a relatively pleasant and flat hike. The route then continues on the Southern Circuit and approaches the summit via Barafu.
It also overlaps a lot with the Lemosho Route, but the altitude profile of the Lemosho Route is much better for acclimatization.