I am curious to know if anyone can shed some light on the difference between ArcGIS' Spatial Join geoprocessing tool (found in Analysis -> Overlay toolbox) and the Spatial Join 'wizard' (found by right-clicking a layer -> Join -> then selecting "Join data from another layer based on spatial location" from the first drop-down).

There have been multiple times where the tool has worked and the other has failed and vice versa, especially when using ModelBuilder and Python.