I use the deck lights only while sitting still: anchored or at the dock.
I too would think they would be a hinderance while underway.
They can be nice tools for seeing a bit better on the deck.
I have also used it at anchor for a few hours to help make us more visible in a strange anchorage but only in addition to our anchor light. Heavy on the amps, but I felt safer.
As far as spotlights, we stick with the $30 hand-held. Easier to use and a lot less expensive when you consider all you would have to do to run power etc. Plus, my wife loves her duty as spot-light navigator. She takes it very seriously.
Courtney is My Hero
If a man is to be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most - E.B. White