Consider the case of someone getting their information by triggering some sort of debug mode on the router, or using some sort of side channel. More plausibly,

Consider the case of someone getting their information by triggering some sort of debug mode on the router, or using some sort of side channel. More plausibly, consider the case where someone can break your over-the-air encryption (but not in real-time). It may be extremely rare, but strictly speaking it's not impossible. That said, if option A may help in some unusual case, and option B will be effective in all non-catastrophic cases, I know which one I'd choose.