Xenon = hot, LED = weird! Let me explain;
If you like your dishes pre-warmed, then Xenon u/c are for you. Mine actually are hot enough to get everything around the warm. Will not that mistake again.
LED's I'm hoping will eventually be the end-all it's hyped up to be, however they're not there yet. Many are made in china, and have poor q.c. on color temperature and output. The american made units are good, they're just expensive now.
I still prefer the new ballast fluorescent tubes. Quiet, good colors, and nice even light distribution!

I chose Kichler xenon under cabinet lighting in my little kitchen because it was whiter than florescent and cooler than halogen. I had halogens in a previous kitchen and hated their heat in the summer. My xenons operate on a rheostat but each fixture has a rocker switch (seen in the photo in the left-hand fixture) that allows you to opt for full or partial power to the individual fixture, putting out the most light where you want it. My installation includes three 3-bulb fixtures and four 2-bulb fixtures. All are hidden in the recess at the base of the cabinets. They do a wonderful job showcasing the movement in my dark granite at night. I love them... one of my best decisions in the remodel. Learned about them on this forum.

Here is a link that might be useful: Xenon under cabinet lighting

Xenon = hot, LED = weird! Let me explain; If you like your dishes pre-warmed, then Xenon u/c are for you. Mine actually are hot enough to get everthing around the warm. Will not that mistake again. LED's I'm hoping will eventually be the end-all it's hyped up to be, however they're not there yet. Many are made in china, and have poor q.c. on color temperature and output. The american made units are good, they're just expensive now.
I still prefer the new ballast fluorescent tubes. Quiet, good colors, and nice even light distribution!

I had the same question about a month ago. Do a search on the lighting forum and you will get some good information.

I opted for the Xenon - they are warm but not hot to me (soften butter but not melt chocolate chips as the lighting guy told me :) I don't leave them on all the time. The light is soft. If you can mount them towards the front of your cabinets - it has better light spread that way, but mine are at the back (long story) and you probably won't notice the different.

Oh yeah - the LEDs I priced were nearly twice the Xenon - I was happy at the end of the project to cut costs.

I did NSL xenon. Warm but not hot. No effect on what's in the cab above. Benefit: I put the pizza dough on the toaster oven and the warmth helps it rise. That's one of the probs w/ my soapstone -- the pizza dough doesn't rise when I put it directly on it. . .

LED's aren't weird! I bought natural white and the color is really warm and nice. I am really pleased. I can dim them for ambiance and turn them up for extreme task lighting. They weren't cheap, but not outrageous either. I posted a thread on how to figure it out and also posted good value vendors. See below.

Here is a link that might be useful: led ucl diy

We used Xenon under cabinet fixtures by American Lighting, in a bronze finish. They are also available in white and brushed steel. Thin enough to hide behind a light rail moulding, line voltage, and dimmable. They have a high/low/off switch, so we never bothered to put them on a dimmer. They can be a bit warm, but never hot. In fact we really don't notice them at all. The fixtures were purchased on the net at Pegasus Lighting.

Here is a link that might be useful: Under cabinet task lighting.

If we could have afforded the LEDs, we would definitely have gone in that direction.

Much more energy efficient, and lighting quality has improved dramatically in the past few years.

We put Xenon under cabinet lighting in the kitchen when we built our house 14 years ago. I like the hi-lo rocker switches that allow bright task lighting or lower, better ambiance-lighting. The lights do tend to run hot but that hasn't been really problematic. The light is fine - not too warm or cool. LED didn't exist as an option when we made our choice - but Xenon was a clear improvement over the fluorescent option (although fluorescents are supposed to have improved dramatically since then). I guess the best thing about the Xenon lights is that we have run them pretty much continuously for 14 years and have NEVER had to replace a bulb!

I gave myself a good burn on the back of my hand while installing a stainless steel wall covering under the range hood. Brief contact while reaching for a tool was all it took. The lights must have been Xenon or halogen but my company didn't supply the appliances so I don't know for sure. They were hot!

So I prefer LED.

Funny this old thread has resurfaced... We just made this choice about a week ago. There was a significant cost difference between Xenon and LED. We're talking $250 for Xenon and about $1500 for LED (not including installation which is the same for both). We did end up going with LED, mainly because of the heat issue, but also because I had just happened to choose a much less expensive faucet so I had some budget wiggle room. I'm still not entirely convinced that LED is worth the extra $1250; I have a few weeks to change my mind and I may.

My sister just switched from halogen to LED. She is fairly unhappy with the LED. She said that they "look nice", but that the light is not bright. She said that with the halogens, she never had to use overhead lighting, UCL was enough for her to do whatever needed doing in the kitchen. Now, she has to use the overheads. Nevertheless, I'm in the process of trying to make that decision...

My KD spec'd halogen lights for the recessed lights, LED for the UC. My electrician said the halogen would be extremely hot. He insisted that I go look at the LED for the recessed lights. He said, while not cheap, the LED would last forever and be cost effective. We went over to Lowe's. They had a display that showed four different colors of LED. I let my husband choose. He selected the soft white. I hope we made the right decision. I'll admit that lighting has gotten really complicated. I miss my incandescent bulbs.

LEDs have improved considerably, and become less expensive, since the OP was written.

You can get warm white, bright white and a really warm yellowish tone.

Halogen are extremely hot. So are the xenon lights which I have below a plate rack in a very low profile strip.

LED has equal brightness, no heat and use a fraction of the electricity. But it's complicated because it's emerging technology and there are no industry standards for bulbs and dimmers yet. I would trust the electrician, not the KD on this. I'm looking at having to redo all my switches in the house to covert to 100% LED -- which are fabulous. Biggest surprise is how great they are.

I just got off the phone with CS at Diode LED. We are looking to install their Dazzle 24 tape light. It will be our task lighting as well as ambient. I haven't gotten the pricing yet but our kitchen is very small so we can splurge.

http://www.diodeled.com/dazzle-24-24v-rgbw-led-tape-light/

santabarbaratara, please report back after you get them installed. I much prefer LED, but I like a very warm white (like incandescent) and I find that generally speaking mono colored LED runs yellow rather than orange at lower Kelvin temps and I don't like that. I'm wondering if something like what you're getting would let you create the exact color you want.

I just had the Xenon under cabinet lights installed. Highly recommended by a trusted long time electrician. They do burn warm no question. To the point where if you have them wide open for 10 minutes, you will burn your hand. There is a high low switch on each fixture which I have not played with which could cool them down a bit. These lights are on a dimmer. My only concern is what is this heat doing to my new cabinets? Having said that, he is installing Xenon lights in multi million dollar houses for people that have unlimited budgets that can afford anything. It seems that most people, including myself, like that warm light that the Xenon gives off vs the cold light that the best of LED's offer. This electrician, who can install any light he wants, uses them and said that he has not replaced a bulb in the last 4 years of steady use. The light temperature is beautiful and does not cast a flare of light that many LED's do. Hope that helps someone...

I can't help but wonder what kind of Xenon light people have who are complaining of them being so hot! I put mine in 13 years ago, and I love them. My fixtures can use either bulb - lighting store once sold me LED bulbs by mistake - hated them - not nearly as bright - returned them.

Well the lights I have are Xenon bulbs and they definitely get hot for sure. They look awesome. They are connected with a dimmer and also have a high and low switch on each fixture. Not sure if that would make a diff with the heat that the bulb is giving out

They were just installed today. I was just not expecting the heat output because everyone talks about how LEDS emit zero heat and i thought the Xenon would do the same. I would rather have the look of the Xenon bulb over the LED any day

We've had our Xenon under cabinet lights since our house was built 15 years ago and have yet to change a bulb! I leave them on in the "low" position 24/7 - I turn them up occasionally to high when needed for tasks. They do produce heat but I haven't found that to be problematic. The cabinets above generally hold dishes/glasses etc - not food - so I don't know if that would cause a problem. I don't regret going with the Xenon and am amazed that not one bulb has burned out in 15 years.

Diane thank you for your thoughts and opinion. Much apreciated