LED is perfect for handheld and backup lights. Their higher effieciency means more light for any given set of batteries. There is no real drawback except limits on output at current technology.
The output from an an LED is bluer than than a Xenon bulb's, and seems to create increased contrast with deeper shadow, but that might be my imagination.
The beam pattern vaires light to light depending more on the optics than the type of bulb used, so it's something to consider whatever you buy.
In the end, buy whatever works for you, but for night diving in high viz on tropical reefs don't think that brighter is always better. My best night dives have been lit by the moon and my LED mini Q40 light, allowing my eyes to adjust to the low ambient light. I use the light only to pick up reflective attention getters like shrimp eyes, and as a focusing light for my camera. This way I don't scare off the critters and with my eyes adjusted see far more than I ever did with a bright dive light.
