Originally Posted by Andrew H.
This is correct.
This was the conventional wisdom 5 years or so ago; I don't know if it's still the case.
Speaking only from own personal experience, Tomtom US maps have improved considerably over the last couple years, or at least, long standing errors here in the North Eastern megalopolis have finally been corrected.
When I was at my wits end a few years ago, and about to dump my Tomtom for a Garmin, I borrowed a friend's Garmin and quickly found many different errors, so who knows.
The most egregious issues I personally ran into with my Tomtom was in Philadelphia, as it had all incorrect knowledge of one way streets, and listed many one-horse-width alleys as navigable streets. I haven't been back to Philly to compare since then.