Outdoor plants can get much bigger than indoor plants. However, they are also more vulnerable to pests, disease, mold and being pollinated by nearby males (nearby being within a couple of miles). You have total control of the environment indoors; you sacrifice that control outdoors, but then you also have some chance of a really big yield too. Outdoors is a gamble with the environment, so if you like to gamble, give it a shot. If you like reliability and control, I think indoors is better.