When you are picking lights for your preferences the technology of light you use generally does not matter much. Sure there are drawbacks and positives to many types of light but as long as you are not putting more light then your fish can be comfortable with and you are not overheating your tank and algae hasnt taken over then anything goes. This changes when you move to a planted or coral tank. When you get into this world you need to meet certain requirements for photosynthesis. There are then many more complication including fertilization, CO2 or other available carbon sources, trimming plants etc.
Plants need what is called Photo Active Radiation or PAR. This is the measurement of ultraviolet light that penetrates into the water and reaches the leaves of the plants (or coral). Depending on the height of the plant this can vary greatly. Normally lights are marked in watts and lumens. Watts is a measure of the amount of electric used and in the same type of lighting can be used to determine a brighter light. Lumens as a measurement is a better measurement in the visible light from one technology to another. It does not give you information though on which portions of the light spectrum are present. When you buy specialty lighting for aquariums this commonly is marked in degrees Kelvin. The Kelvin scale is the visible color that (do not remember if it's) hydrogen (or something else... anyone knows for sure let me know) burns at different numerical temperatures. This thus means cooler temperatures such as 4000-6000 are more yellow while those in the 9000-10000K range are more white and eventually blue.
Types of lighting that are acceptable over plants/coral? In the 1-2 gallon range you can sometimes get away with common incandescant technology lighting. After that in the 2-5 gallon range you need to use either normal flourescent strip lighting or screw in compact flourescent. Compact flourescent (CF) is also known as Power Compact or PC lighting. Compact technology is where they pretty much take a normal flourescent and fold it into a U shape straight or twist it after it's been put into a U so that there is a single ended plug. It then takes up about half the space and is commonly driven at the same or slightly higher wattage to glow brighter. These come in a large variety of lengths. Once you get into the 5-20 gallon range you can usually use CF strips as well as special multi bulb normal flourscent as well as a more recent "normal" flourescent light type called T5. T5 indicates the diameter of the light. This is representative of an approximately 1/2 inch diameter tube. Another common size is the T8 bulb.
Once you get over 20 gallons you have a large variety of fixtures and technologies depending on fans for cooling, where the lights will be mounted, the size of your tank, and more. In planted tanks you generally find somewhere between 2-5 watts per gallon of CF/PC lighting potentially coupled with T5 and finally ending up with Metal Halide (MH) fixtures when you get to the upper end of very large tanks (1000 gallon etc). Other options include High Output (HO) and Very High Output (VHO) flourescent which look like normal flourescent bulbs with special internal parts as well as high power ballasts to drive them brighter. Side effects of HO and VHO as well as large amounts of any type of bulb is heat. Without proper ventilation temperatures will rise significantly in the tank resulting in the need for cooling devices such as a chiller. Most plant tanks need something near "Normal Daylight" spectrum lighting which is in the 6500K range.
With coral tanks depending on whether you are growing hard or soft coral will tell you how many watts and the technology your tank will need based on size of tank, mounting distance for the light, and depth of tank to reach the coral. Even in smaller sized tanks with coral you generally run more then one type of light in high wattage. Heat is almost always a problem and most people running salt tanks have chillers when they run small tanks since most small tanks have tightly fitting lids on and the lights rest on top of the lid. With larger tanks the spacing of the light from the surface is usually coupled with an open top so the heat increase is limited.