I've used a 21w LED Salvo back to back with my old 21w HID Salvo for a dive in Madison Blue. I used the LED on the way in and the HID on the way out.

The compactness of the head and the colour temp of the LED are superb - but it still doesn't focus and have the pencil type beam that you get with the HID. The beam is much less defined and the halo is too great IMO. HID is far better suited to cave diving still - although I don't think that the time when that is no longer the case is that far away. The efficiency and ability to focus LED seems to be improving almost faster than anyone can keep track

LED is great for a small ocean diving light - particularly for someone who travels and values the compactness and the lack of weight compared to HID

HTH and "Happy Birthday, Joe. Hope you get lucky" ditto