True where the bulb is more susceptible to busting the filament, dropping it on pavement seems to be the only issue i have seen with the 50w LM. My friend takes his on just about every dive, using it while lobster hunting, wreck diving, reef diving, he is NOT gentle with his light.
The efficiency is currently only better by 2-4 watts (I think for every 10 watts), sure the led is efficient but, the driver which provides regulated power is normally only 83-87% efficient(17-13% energy loss normally for total watts).