Ah so you collude with capitalists who ignore laws to save a few quid - not a very strong moral position.
1) Worse to use (standing in the rain with you arm out in the hopes someone will stop, let alone trying to get one on a side street)
2) Based around getting lost (taxi drivers are too arrogant to use technology so will drive into roadworks and traffic jams when modern cars use things like waze or whatever to avoid them)
3) More expensive
4) Less safe (who's driving? Who knows! Lets hope it's not John Worboys)
The fact that Uber hasn't yet broken laws in the UK doesn't make using them more defensible. Would you accept a babysitter that only abused children when on holiday in Thailand?
Undermining unionisation and actively promoting the casualisation of labour in the way they have are to be discouraged whether legal or not.