Hey Mike,
HID lights are great lights with lots of "punch" through the darkness. So we like them a lot for cave diving do the the focusable beam that is tighter than an LED. They cut through a dark cave or a dark wreck with gusto. However, an HID is not as robust. The bulbs can break if the light is dropped or banged against a tank (think churning dive boat). You don't have to baby them, but you have to be more aware of them.
The LED lights are robust and with the LUX's entrance on the market, you'd also be getting a bright light. LEDs use an array of diodes vs. bulbs and due to the nature of the diodes working together, you don't get quite the punch since they aren't able to get as closely focused as a single bulb. However, they are robust and can take more of a beating.
I'd be tempted to go LED in your shoes, although you won't be disappointed either way. Both lights will provide excellent illumination for your dive conditions. Bit of a toss up, but the robust nature of LED with 6 hour burn time is probably your best bet.
Hope this helps,
Kathleen
