When I did a complete remodel of our kitchen some nine years ago, I elected to go with LED lighting. It was cutting edge technology at the thime. Although they were more efficient at the time than halogen, they had ways to go.
Today, LED is arguably the most efficient lighting available, running in the 140 lumen/watt range. Often, efficiency is rated in terms of efficacy. LED lighting is fundamentally different than other lighting in that it projects the light in one direction, typically a 120 degree cone, as opposed to nearly 360 degree radiation of incandescent and fluorescent lights. Back light has to be reflected to be useful in most case and there are losses associated with that. Because the LED's provide a greater percentage of useful light, their output seems higher than it actually is. They use efficacy to describe the useful light output. I used warm white LED's, (~3000K) for ambiance but the cool white are the most efficient.
LED's are low voltage DC devices and regular household current has to be transformed. Standard transformers have energy losses associated with them which reduces overall efficiency. Additionally, LED's have to have current limitation provided to prevent thermal runaway and self destruction. This is most simply done by placing a ballast resistor in series with an LED string. These resistors transform electrical energy into heat, again reducing the overall efficiency. Great strides have been made in the driver circuitry for them. Modern LED drivers usually use some sort of switching technology to drive the LED's. This typically runs more efficiently than other forms.
I always look for light output on any LED I buy. Don't trust high intensity claims unless they are backed up by specs. Commercial LED lighting providers use two metrics to describe their product; equivalent light output and actual output. Equivalent output is usually compared to a standard incandescent bulb (40 watt, 60 watt). Fluorescent replacements usually give actual lumen output. T12 fluorescent lamps typically have a an output of around 3500 lumens for a 40 watt lamp. If you want an equivalent amount of light in your replacement fixture, you should be looking at this as a guideline.
For the more adventurous, there is LED strip lighting. I used this on our front porch instead of fluorescent lamps. A five meter strip replaced four fluorescents. My wife insisted that I put a dimmier on them because they were too bright. They are found in strips running up to 5 meters long. They have a self adhesive backing and run on 12 volts dc with built-in driver circuitry. They can be cut at intervals of 3 LED's, usually about 1-1/2" and the can be connected together to make longer runs. I mount them on an aluminum backing, 1/8 x 2" flat or 1/2" aluminum channel (sold as plywood edging at the local DIY). It helps with heat sinking which increases light output and service life and should replacement be necessary, makes for easier work. Replacement of defective LED's, should that happen is done by cutting out the bank(s) of three and solderingng the replacement. This is something I have yet to do. I provide the 12 volt dc power with high efficiency switching power supplies which are quite economical now.
LED Supply sells drop in replacements for 4' fluorescent's. Environmental Lights also sells commercial fixtures for area lighting. Both are on-line and companies I have had excellent service from.
Bottom line: LED lighting is more efficient but it is still quite pricey compared to other forms. I have fluorescent lighting in my shop and am not contemplating replacement of same at this time because the incremental savings in electricity for LED replacements is not that great yet. I have replaced almost all incandescent lighting however and will use LED lighting for all new projects. The LED technology and the driver technology are both making great advances. Costs will come down in the near future, due to improved technology and volume manufacturing. It may be advisable to wait a few years to be able to take advantage of forthcoming advances.
A factoid: Not many people realize that white LED's are fluorescent devices. They replace the mercury vapor excitation with blue LED excitation. Much off the efficiency gains in recent years had to do with developing better phosphors.