The CXB3590 is 51.7% efficient driven at 50W. The very best HPS is the 1000W DE philips bulb, approx 41.5% efficient with brand new bulb. Standard 600 and 1000W HPS bulbs are ~36-38% efficient when brand new.
However, these numbers cannot be directly compared, they are just the starting point. HPS loses a lot due to reflector loss, spectral spread, bulb depreciation, reflector depreciation, hot spots. Air cooled hoods get several more penalties due to losses as they reflector off and pass through the glass, film/dust buildup on the glass and according to Jair from Gavita, incorrect bulb temperature.