I get the feeling this will be a popular thread here. I get both sides but I feel like it even's itself out. Here is my reasoning.  With a greenhouse you don't have to really worry about animals eating your plants and helps with bugs. Downside the ventilation isn't as good and you don't get the direct sunlight. Greenhouse in this case has pots which limits the size potential, whereas outside with direct sunlight but no pots no size limit.