"As far as efficiency goes there doesn't look to be much difference at the moment between sodium vapor lights and LED lights."
Strangely your reference actually states: "For example, a 30W LED street light can often replace an 80W High Pressure Sodium lamp. The reason for this is directionality. LED street lamps are very directional and the light output is much more even then by other street lamps."
Apart from that, I suspect that HPS lights are difficult to make efficient at low light outputs, such as what you need for narrow streets and footpaths where a high-power lamp mounted high up would spill too much light outside the road.