In my case, as to the nav lights, the only one that would make sense to change to an LED is my combination 'all round/masthead' light, as this is the only one that would be on if the engines were not running.
I have no need to change the red/green nav lights to LEDs as those would only be on while underway, which means the engines would be running, and there would be plenty of power to run them, so why change them?

I haven't found a good combination LED "all around/masthead" LED light yet that will fit my boat, so I haven't updated it yet.
I did change almost all of my interior lamps from halogen lamps to warm white LED lamps. It makes the fixtures a lot cooler and I saved a boatload of battery current (went from about a 20 Amp draw with them all on, down to less than 2 Amps!).