How can you be sure of this? When you're dependent on an organization for your paycheck, it's best not to say bad things about that organization, whether you actively suspect someone of being an auditor or not.
Granted, neither company is a paradise for a would-be driver. I'm sure they all have their complaints. It's essentially a customer-service position, and their have been plenty of threads on here discussing the downsides of either company.
Regardless, again, many of them are content with their job, and the lifestyle it incurs. Most drivers I've spoken to are animated when talking about setting their own hours, "being their own boss", and many even are animated in discussing company politics or current events regarding them. Don't take my word for it, though, actually talk and get to know your drivers; an abstracted analysis or a news article isn't the best way to get an impression of the situation.