Led lamps have been a growing part of marine lighting technology for about the last 5-6yrs--pros: brighter light, minimal amp/power draw for given wattage of a comparable 12v incandescent, no heat build-up,extremely long life--cons: expensive, initialy--I used Leds on my running lights and anchor light on my sailboat for about 4 yrs never had to replace one, whereas I frequently had to replace standard bulbs, and Halogens(they dont like lots of motion shock)--on a dark night I could always spot my boat's masthead led anchor light at a crowed anchorage from shore because it looked like Venus among the other stars because it was so bright.
I used Halogens and they work great, bright, relatively in expensive, but they have a short life if exposed to moisture or motion shock---because of the heat they can melt plastic lens coverings and they draw lots of amps for the same wattage 12v incandescent.
The 1127 style led bulbs I've seen in use in some H/D trucks and cars are much more visible from behind and up to 90deg on the side, depending upon the vechicle's lens refraction.
I used a 1150(?) single filament Led for my anchor light about $30--the dual element 1157 led was about $40 at West Marine--about 4-5 years ago--they are 12v auto style bayonet bulbs--
I've looked into automotive Leds and the prices are $$$$heavy-
Think I may go to the Chandlerey and buy my Leds
