I may go against the grain here and suggest that the broadhead is deadlier with a double lung at short range, at least in my experience. Even though I use premium expanding bullets on deer, not FMJ, any deer that I've hit through the lungs with them has taken off, as they often will.(I shot a big doe through the lungs with a Accu-Bond in .300 WSM that went 50 yards.) They are still dead on their feet of course, and easily recovered. However, When I shoot a nice, sharp broadhead clean through the pumphouse, the deer isn't even often unalarmed, even as the arrow has passed completelythrough, and simply run off a few steps and fall over. I have had one that went back to feeding for a few seconds and simply fell over.
As we know, any holes that are put into the lungs are fatal. I know that the FMJ can tumble and cause damage, but I have seen pretty devastating kills with a well-placed broadhead. (By the way, the ones I use cut a full 2") All other things being equal, I think that a well placed broadhead is deadlier than a .308 FMJ. I know that some may disagree, but this has been my experiece.