Quality is not entirely dependent on indoor vs. outdoor. That said, a grower equally proficient in indoor and outdoor techniques with equal access to optimal space and equipment for both will be able to produce more delicate, "higher-grade" flowers inside.

Cannabis grown outside with quality organic nutrients that is properly flushed is delicious and potent, but it does have to contend with the elements. You tend to have more robust plant material in your buds, which can lead to a harsher smoke.