The implication being that the choice is let Benitez spend, or sack Benitez?
Because honestly, I think that's what it comes down to. The window we spend in - January or summer - is less material than who spends the money. Despite the arguments about value for money in January.
Personally, I think this is a rough patch Benitez will get through, and things will start to pick up again. I'd rather Benitez, as a manager who has seen the weaknesses in the squad first hand, has a say in patching those holes, as opposed to a whole new manager who would need to learn the same hard truths about the squad.
I'm discounting Brands in this discussion, because he's either doing badly, or not being allowed to be a Director of Football. Like you say, we don't know.