Short answer: Compare both routes for the same car and practice period. There is no universal winner: the relevant facts include total payable cost, policy terms, claims impact and the learner’s expected test date.
Adding the learner
The existing insurer can explain the premium change, excess, named-driver terms, mid-term fees and renewal consequences. Ask whether a learner claim could affect the policyholder’s no-claims discount.
Separate learner cover
A separate policy may sit alongside the car owner’s annual cover. Check whether that arrangement is permitted, whether the vehicle must remain insured, which claims affect which policy and who handles an incident.
Compare on one page
Record identical dates, total premiums, fees, excesses, cancellation terms, vehicle-use rules, supervisor criteria and pass-test treatment. Comparing a monthly payment with a short-policy total can be misleading.