Although I am not familiar with the product to which you refer, I very much doubt that two flourescent lamps each of 24 watts will produce as much light as a 150 watt metal halide.
Flourescent lighting is often more efficient than metal halide, but only by a relativly small margin.
Flourescent does not have three times the efficiency of metal halide, which is what would be suggested by the above.
It is of course possible that the flourescent luminaire better focusses or directs the light, such that the light level is comparable to metal halide directly below the lamp, or within a certain beam angle.
However the reduced total output would mean less light emitted in other directions, this may or may not matter depending on the application.
Or the supplier may mean that the flourescent light gives the same output as a 150 watt HALOGEN. Metal halide and halogen are very different, but are sometimes confused especialy in imported equipment.
