Philippa says

AFirstly, it is important to say both those numbers are high; scientists were aiming for over 50% effectiveness and both vaccines you mention are above that. You are unlikely to be able to choose – having the vaccine said to be 70-90% effective doesn’t mean it is less likely to work. They can’t be compared directly as they work differently and the studies were different – one stated you would have COVID-19 if you had a positive test and one symptom, while the other said you needed a positive test and two symptoms. Rest assured both vaccines give excellent protection.