A good light should provide you with enough lumens to easily handle the type of diving you're into. Lumens are the internationally recognised way of measuring light output.  If the light you're considering does not show its Lumen reading, we would recommend caution.

We offer ultra powerful underwater lights from the 700 lumen Maxbright LED of the Princeton TEC Sector 7 to the Atlantis L1-900, an Aluminium 900 lumen dive light
You should also consider features like LED, a water depth rating, burn-time and warranty back up. 

Thanks for taking the time to view our selection of Lights.