I think this is the most controversial topic around growing cannabis and it is very difficult to find a good side by side comparison online. I plan to do one on my next grow.
At the moment I defoliate. My thought is that it will increase air flow and will direct the plants energy to the appropriate place. I generally do a first defoliation right before flower and then another after 21 days.
Hopefully this helps! Happy Growing!
I think it's always best to do it at least once in flower. Shades are more for protecting the "fruit" buds from burning in the sun. As your controlling the environment they're not nessasary. She pulls energy from the canopy shades and the leaf in the buds.