There are advantages to both light sources.
With Mother Nature's sun, you know they are getting 100% of natural spectrum for these plants to flourish, both veg and flowering. The disadvantage is lack of privacy, weather elements, robbers, and bugs. Personally, my babies always look more natural and thrive under the sun.
With HID's, you can manipulate your growth and timing in stealth mode. But you also face other shit, like higher electric bill, power surges and outages, and heat build-up inside the area. And for some reason, my indoor grows always produce twisted leaves, which doesn't kill them, but it looks awkward.
My current grow is both. I put the girls out in the daily sun, and then bring them in when the sun goes down for 24/0 veg period. The results are very very good so far. I will post the outcome when I hemo da girls.
Aloha brudahs and sistahs!!