|Public sculptures were a highlight of the tour|
That's likely due to the format: when the guide has to rely on tips to make a living, you can be darn sure he's going to hone his patter to a high gloss. So these tours are consistently entertaining.
But I've also found them to offer a more pointed and enlightening commentary on modern life in the destination than you're likely to find with less informal tours, perhaps because corporate bus and walking tours have more of a stake in keeping the local tourist boards happy. So they censor tour content (this is a guess, I'll grant you), keeping it peppy and upbeat. The free guides, I've found, are more likely to tell it the way it is.
That was certainly the case with the Tour Guys jaunt I recently took in Vancouver. Led by a towhead named Max, who'd graduated from college just the week before, the tour covered everything from local history to gossip on the city's crazy housing market to speculations on what would happen should the Vancouver be hit with an earthquake (it sits on a fault and seismologists worry that it's overdue for a trembler).
Frankly, the tour was far more fun that it should have been, as we did it in a steady downpour, made worse by chill winds. But Max didn't lose a single one of his ten participants, and kept us chuckling throughout, no small feat. Highly recommended.