The trouble with such statements is that they are of no significant value in relation to individuals. Whilst it may well be true that licensed drivers driving licensed cabs are, 'in general', better/safer, a particular licenced driver driving a licensed cab might be much 'worse' and much less safe than another particular one who was unlicensed and driving an unlicensed cab.but compared to somone with NO license, driving an UNlicenced cab, who doesn't meet the minimum requirements for cabbing and is therefore uninsured...
Only 'personal recommendation' (from people you know and trust) is really the answer - whether one is talking about cab drivers or electricians!
Kind Regards, John