I dunno either...my humidity has stayed pretty high so it hasn't really been a question yet for me, but I was kinda wondering the same thing, sorry I can't help. Anybody....?
prolly a weaker bud. i read somewhere that only during flowering does it matter. i think it gives the veg stages more of a danky smell and a more even growth.
I would say that could make sense, I imagine humidity probably wouldn't single handedly kill a plant unless it was 0 all the time or 100 all the time...