I wouldn't know, but everything I've grown outdoor has an extra layer of potency with more unique smells than anything I've grown indoor or had from friends indoor setups. Plus why burn tons of coal to grow some weed indoor when you can grow more an better outdoors for practically nothing.
Outdoor is easier to grow in the sense that nature takes care of a lot of beginner mistakes for people - which could therefore increase quality.
Don't get me wrong, I by far prefer growing outdoors, but I think it's hard to beat indoor quality (if you have everything set up/dialed in properly) unless your growing greenhouse outdoors. Indoors you can create a perfect environment for plants. Perfect temp, humidity, etc. biggest advantage to outdoors is you can't beat the sun. Hence, an environmentally controlled greenhouse will beat both outs & ins. You can supplement light there to for those cloudy days..
I just don't really understand where the argument comes from. Seems like common sense. I've seen thousands of pounds over many years grown both outdoors and indoors in Cali, Oregon, Washington & Colorado. In all states, the indoor has always won as far as appearance, smell & taste (assuming the grower of both is good - a pro grower outdoors can produce better outs then someone who is semi-good to good indoors, but have that pro grower grow an indoor an outdoor crop, the ins will come out better). Seems like it's always the outdoor growers who sell outdoor that say outdoor is so much better... I just like to smoke whatever taste the best & is the most potent, so that's what I've always gone for.
To each their own..