Most plants need lots of light in order to grow, since light is their source of energy. Note that I said *most* plants - too much light can be damaging to plants, and plants adapted to living inside of forests under the shade of trees make do with less light than plants in the direct sun. These dark-loving plants may actually grow better in houses - houses with windows of course because they do need some light - than outside in the open sun.

I think it would actually partially depend on the kind of plant you're trying to grow, what part of the world you're trying to grow it in, and what time of year it is. For instance, trying to grow a tropical plant outdoors in the arctic tundra may not be very effective! Be careful when making generalizations :) But in general, I think plants that grow outside have a better source of nutrients from soil and direct sunlight -- which is what they need to grow. Hope this helps!