I would go for a Financial DD over HR DD.
The risks of acquiring a company with bad people and cultural fit are distrust, resistance to change and attrition. Even in the case of most specialized skillset, the ability to replace talent might still exist. It may take longer lead time.
However, the risks of acquiring a company with financial inappropriateness impacts the results of the company in the immediate quarter. What’s worst, financial irregularities exposes the acquirer directly to the regulators resulting in scrutiny and penalties.