The audit is not the enemy. A proper audit or verification examines things software cannot — it applies professional scepticism to your claims, not just your configuration. Its weakness is arithmetic: it happens on one day, and regulatory risk accrues on the other 364. A finding that appears in March waits a year to be found.
The consultant is not the enemy either. Judgment is exactly what you should pay a professional for. The mismatch is using professional hours for vigilance work — paying advisory rates for someone to check whether a deadline moved or a register is current. That is monitoring, and monitoring is what software does at a frequency and price a retainer cannot match.
The spreadsheet is the honest default, and the most dangerous of the four — not because it is wrong, but because nothing tells you when it becomes wrong. It fails silently, and it fails completely the day its owner resigns.
The pattern that works: continuous monitoring as the base layer, professionals for judgment, and the annual audit as the external check it was always meant to be — a confirmation of what you already knew, not a discovery of what you missed.