Lighting is a complicated subject, but I can probably explain a few basics that will help answer your question.
You don't mention live plants, but aquarium light for plants must be quite specific. It must be a minimum intensity to drive photosynthesis (how plants grow), and it must also provide good wavelengths in the red and blue colour (these drive photosynthesis directly, red more importantly) and adding green to the mix helps plants and also improves the colour rendition, making fish and plant colours more natural. Other than intensity, fish don't really care about the light; intensity is important because fish are directly affected by intense light. Most of our fish come from fairly dimly-lit waters, and their metabolism and physiology is designed for this.
To compare lighting, we need to know the purpose (plants or just fish, and if plants, which species because different species have differing light requirements), and the intensity and spectrum of the light bulb/tube/LED output. Watts is only the measure of the amount of energy (= electricity) a bulb/tube needs to produce the light it emits; unless we are comparing identically-manufactured bulbs or tubes, watts is not an indicator of intensity. Example, a GE Daylight 6500K CFL bulb of 13w will be brighter (= more light intensity emitted) than the same bulb in 9w. But this 9w might be much brighter light than a different brand bulb in 20w. These days, bulbs and tubes are manufactured very differently, so it is how the bulb/tube is made that determines the light intensity and spectrum.
If you could provide more data on the Interpet bulb I might be able to be more specific; also, are live plants present and which species. I use the less expensive home improvement/hardware store bulbs whenever I can over aquarium-specific ones, but this may not always be possible depending upon the bulb/tube.
Byron.
