Short answer: Match both options to the same expected practice window, then compare total payable amounts and policy terms. Repeated short periods can add up, while annual cover can include cancellation rules and unused time.
Temporary cover
Short cover can run for hours, days, weeks or months depending on the provider. Check start and end times, extensions, repeat-purchase rules, fees and whether a test is included.
Annual cover
Annual cover can be paid once or sometimes by instalments. Monthly payment does not necessarily mean monthly insurance. Check the total credit cost, cancellation calculation and pass-test treatment.
Use realistic dates
Estimate the likely practice pattern and allow for a delayed test. Compare totals for those dates rather than dividing an annual premium by 365 or comparing it with a single day.