Not all plants grow faster with more light as it depends also on available nutrients, the type of plant, the season, the temperature, etc. The studies I've seen on Pothos indicated that 3,500 foot candles was more productive in quantity of vines and weight of the plant than 5,500 ft-c regardless of available nutrients. (See the MREC studies.)
Like medicine, there's an optimal amount, and more is not only not always better, but sometimes is much worse.
http://mrec.ifas.ufl.edu/Foliage/Resrpts/rh_91_11.htm
http://mrec.ifas.ufl.edu/Foliage/Resrpts/rh_92_16.htm
http://fshs.org/proceedings-o/1990-vol-103/176-178 (REYES).pdf
- 1,000 - 2,000: bright but indirect sunlight, may not produce a clearly defined shadow, but is good for many types of plants that require indirect sunlight
- 2,000 - 4,000: About 40% of midday sun, or direct light coming through windows, bright light and appropriate for plants that require good, strong light intensity
- 4,000 - 5,000: About 50% of midday sun, or strong direct sunlight in a bright room, good for plants with high light requirements
- 5,000 and up: Very bright indoor light