I think defoliating or the advantages/disadvantages are dependant on the way you grow your plant. Leafs however do not take nutrients or "leach" energy, a leaf is the plants solar panel. A leaf takes in gasses and creates sugars for the plant to grow. A leaf either works for the plant or (when not catching light) does "nothing".
Leafs however can obstruct airflow which can give disease issues.
What many people tend to forget is that when in need a plant cannabilises itself, starting with it's least important parts, in the flower stage, that's the lower leafs... so those are her buffer when you f*ck something up..
If one doesn't want popcorn buds just remove the lower nodes.. if they don't reach the cannopy they're not worth the energy the plant puts in if you'd ask me. This way the plant can focus it's energy on it's big buds and you open up the plant to put those lower leaves to work, supporting your big buds in the cannopy.
I'd say the gear u you use and the way you shape your plants during vedge determine if you can take advantage of the lower leafs or are just as well off just cutting them off.
I only take off two leafs per plant per cycle, the two fan leafs that shade my two main colas after topping, that opens her up enough to let 4 colas pass through the center of the plant, the two below those four go along the "outside" making all 6 reach the top of the cannopy before the flower stretch is over so they all get some serious lighting to fatten up and airflow so I don't have budrot issues. I take the bottom two nodes clean off before starting the flower lighting. I grow sativa's and indicas in the same box and by the looks of them you couldn't tell them apart... (Except of course by the leafs, which I leave on

)
I feel that if you interfere with your plants natural way off things you should have a very deep and profound understanding of the how and why, cause and effect on a molecular level so to say, don't do shit because people on the internet do it too..
Peace !