I feel like this topic is so hotly debated due to the fact that it is all grower preference.
I dont believe in defol during veg i feel it just slows the growth. HOWEVER; i do feel that defol can be used during veg to control bud sites. Here is a link from Grow Weed Easy about Mainlining.
http://www.growweedeasy.com/mainlining-nugbuckets
Im in the last few weeks of a grow right now. Once im done my next round i am going to grow 2 white widow side by side and main line them. 1 i will defol like in that tutorial, 1 i will leave alone just to see for myself.
i also think as someone said earlier its very strain and situation dependant. All plants react differently. Just gotta check and see for yourself.
It's always worth a try.