I have the
Sartek 10 watt adjustable and am quite happy with it. I purchased it at
Ginnie Springs. When I was in the store I was able to compare it with the equivalent 10 watt adjustables from DiveRite and Halcyon.
I felt that the DiveRite had the best looking light output, a nice even field. The Halcyon had optics that were not quite as good due to the smaller reflector. The Sartek had similar light output to the Halcyon but had the most rugged light head and battery canister. Since it was more important to me that the light continue to work after being packed in a suitcase and bouncing along in either a car or airplane, my choice was the Sartek. The DiveRite had the "test tube" and exposed reflector design and while the larger reflector has significant advantages when it comes to light quality the fragile nature of the design ruled this light out.
I have had the light to 150 feet with no problems, and I have used it in caves, again without any problems. The only issues that I have had with the light were my fault, once the light was turned on out of the water for what I thought was just a couple of minutes, but was probably more like an hour. When I went into the cave the battery died near maximum penetration. This was my fault, and we safely made it out with me switching to my first backup light.
Normally when the light stays off between dives I am able to get two or even three dives on a single charge. That is somthing like 2 1/2 to 3 1/2 hours of burn time without any problems.
In a cave more light is not always better. The best wattage light to have is one that is the same as your team mates. Eyes will adjust to the available light, if you have a 21 watt, but your buddy has a 10 watt, your and your buddies eyes will need to constantly adjust to the differences in intensity. If your lights match, even at the lower wattage bulb, the team will be happier.
On night dives in the open water perhaps having the brightest light has advantages. I know that when I have been on open water night dives with other recreational divers I tend to focus the beam into more of a flood pattern so my light does not completley overpower the other divers lights.
Whatever you choose, have fun with it.
Mark Vlahos