This menu is also a remnant from earlier development-days and is no longer used.
By default face-normal extrusion is used which does produce the best results. Spherical extrusion might result in weird stretching issues and is a remnant from earlier development days. Always use face- normal extrusion.
You can lock axis of extrusion so that the extrusion will always look in a certain direction, usually you won't need this feature.