Neither type is significantly more efficient than the other.

Line voltage filaments are not as rugged as low voltage filaments (there is a real reason vehicles use low voltage lights).

Line voltage puck light firmaments can fail from the vibration of moving items (in and out of the cabinet) on the floor of the cabinet above the light.

Thanks brickeyee. Would a "bar" type light filament also be that fragile? I am looking at the Pegasus Xenon Line Votage Thin Under Cabinet Task Lights.

Low voltage fialemtnscan be made as a double helix.

They are twisted up once, then again.

This males them much more rugged.

120 v filaments cannot be twisted very much or the voltage will arc over them when the twist get to close to each other.

If the 1230 V is applied to separate bulbs in the unit they will be vulnerable.

If they are in series when one in the string fails all the bulbs go out, but they can be made a little more resistant since the full 120 V is not across each filament.