Every now and then, I'll grab a cab at Union Station to go north of the River.
My most recent outing was in a god-awful stench of a cab, driven by a guy who spent the entire drive whispering into his Bluetooth device in god knows what language. I was attending a meeting at the Four Seasons. Delaware Street was blocked off just west of the hotel and it was clear that he had no idea how to work his way around the detour and get to the hotel (here's a hint: If Rush Street is one way northbound, going west on Walton from Michigan isn't going to help). He ran at least two red lights when he got messed up and I bailed on him at Rush and Walton when it was clear that the ride was going to involve trial and error for 15 minutes. He got the exact meter for being an idiot.
For a brief while, it actually appeared that the City cared about the taxi system and customer service. That seems to have gone away in favor of doling out hack licenses to anyone with the cash to spare, regardless of language, driving, or navigation ability.
NYC taxis are a notch better, but not by much. I've had a few winners there too (like the guy who was determined to go down a street that the NYPD had blocked off and almost got his window busted in by the cop).
I've been to London a number of times. They have the absolute best cabbies. These guys put out serious money for the business and can lose it all in a moment. They are tested regularly and their cabs are gone over with a fine tooth comb. The fares are not cheap, but I would pay for a clean, safe, stress-free experience in the Loop.
I had a guy in Brussels not pull the flag when we left a train station. When we got to the hotel -- surprise! The meter showed about double what it was going to the train station in rush hour. And his command of English was suddenly non-existent. I had the night manager at the hotel speak with him and got the fare reduced.
So cabbies can be bad just about anywhere.