What each structure actually commits to
An hourly arrangement commits to attendance, not to completion. If the task list takes longer than the hours purchased, the work stops when the time runs out, and the shortfall is either invisible or becomes an additional charge. That can be entirely appropriate where the requirement genuinely varies, but it means the business carries the risk of the estimate being wrong. It also means the business has to keep an eye on what is being achieved each week, which is a management task in itself.
A fixed price against a defined scope commits to the scope. If the work takes longer than the contractor expected, that is their problem provided the scope has not changed. The business carries less risk and gains a checkable document, but it only works when the scope is written properly. A fixed price against a vague list simply moves the ambiguity into the delivery. A scope with vague frequency wording will produce disputes under either structure.
