If your electrician installed line voltage wiring (120V AC) for the under and over cabinet lighting, then low voltage lighting is largely ruled out. Ask your electrician.

If you want inexpensive UCL (under cabinet lighting), go with fluorescent.

If he did install 120V AC, can't he just come back and install a transformer(s)? Just wondering.

How does fluorescent stack up against xenon?

And somewhere on here, I saw a thread that detailed how to choose the right (fluorescent, I think) bulb for the amount of light you want/color of light. Something about some numbers printed on the bulb itself?

Low voltage lighting will need to have separate low voltage wiring from the transformer to the lights.

Fluorescent has lower power consumption and heat output. Some people may complain about the cri color rendition index, humming (magnetic ballast).

The light will most likely be T4 or T5 tubes.The light will have a rating in kelvin which defines the color.
2700 - 3000k warm white
~4000k - cool white
~6000k - daylight

Most people will want something between 2700 - 4000 (warm - cool white).
Visit your local lighting store to see the which you'll prefer.

Excellent! Thank you!

Another thing
most UCL fluorescent lighting is not dimmable.

If dimming is required, you'd need to get the appropriate dimmable electronic ballast (or dimmable UCL fluorescent fixture) and electronic dimming switch.

I looked into dimmable electonic ballasts a couple years ago and could not find suitably priced ones.