You have alot of choises but for kitchens where you spend alot of time
here are a few things to consider. All incandesant bulbs are only apx
90% efficient so they put off 90 % of their wattage in heat. In summer,
with cooking you will be increasing your cooling load, as kitchens look
nice lighted up, but can consume alot of power. Incandesants put out
17-20 LPW -lumen per watt. T 8 flourescent output 60- 100 Lpw and last
much longer and can be dimmed with proper ballast and dimmer. T5 and T8
are common undercabinet lighting and look good with the proper warm
white bulb. Look into flourescents for the long life and energy savings
they offer. New better color flourescents are always being designed ,
but look at 3700-3800K warm whites.
I will guess 12v being less efficient than 17Lpw as the transformer is
waisting energy as heat.