This is a discussion on Unsure about my light within the Beginner Planted Aquarium forums, part of the Beginner Freshwater Aquarium category; -->
I recently bought a 20 gallon aquarium kit by Marineland. It came with an LED light and I was wondering if it would be ...
I have not tried LEDs myself, but I have seen them at a local fish store over nicely planted 20g tanks, and there is no question that the set-up in the store was doing well. I can't say if the units are the same. The one you linked has two rows of LEDs I believe, it may take two of these units.
I would not use the second link, the dual 24-inc fluorescent tube. That is way to much light over a 20g. If you decide on something other than the LED, the best is an incandescent (screw-in bulb) unit with two sockets. These hoods are not expensive, probably cheaper than the LED fixture ($39) but certainly no more. Then you get two Compact Fluorescent daylight bulbs from the hardware store. I use GE 6500K daylight bulbs over my 10g and 20g tanks, and I have two 10w bulbs over each and the plant growth is good.
I actually recently contacted them about the lighting that comes with their kits. I deleted their response or I would post it directly. They told me that the light in the kits is only good for viewing fish, not for growing plants.
Not sure about how much light you should have. If you do some research and find that T5 is good check out Sun Blaze T5 strip light and reflector. They are a very inexpensive light with a good reputation for quality.