I think it all depends on the involvement of the creative team and casting. And sometimes the tour will end up being stronger than its Broadway counterpart.
I saw both Wicked and Phantom on tour before seeing them both on Broadway. In both cases, I found the tour casts to be more impressive on the whole. It seemed like both Broadway casts were sort of phoning it in a bit (with some exceptions). I think traveling around the country and constantly performing for new types of audiences keeps touring actors on their toes both onstage and off.
I'd say it depends on the tour, how long it's been on the road, what kind of schedule they have, etc. Lot of factors involved. (For example, when I caught the original replica production of Phantom on the road several years in, they were so zombified I wanted to hop onstage and check their pulses.) By and large, though, I agree with the assessment that the tour is sometimes stronger than the Broadway company.
I just saw the 2nd National Tour(I think) of Wicked. The cast which included Laurel Harris and Kara Lindsay were MUCH better than Jackie Burns and Chandra Lee Shwartz who were the last pair I saw on broadway. Although I have to say Jackie Burns' vocals were amazing. Also, maybe she's just low energy overall but it felt like Chandra phoned it in when I saw her.
I clearly remember a line from that Christopher Sieber/Benjamin Hickey (?) comedy on TV, from the early 2000's: "Don't judge a show by its touring company." (or something to that effect).
"Noel [Coward] and I were in Paris once. Adjoining rooms, of course. One night, I felt mischievous, so I knocked on Noel's door, and he asked, 'Who is it?' I lowered my voice and said 'Hotel detective. Have you got a gentleman in your room?' He answered, 'Just a minute, I'll ask him.'" (Beatrice Lillie)
For me the worst touring was the last "Cats", not because of the actors, but they were using that horrible inflatable set. It looked like a child's birthday party. While, the set can never be as elaborate as Broadway or it lacks a stage elevator, usually a tour is similar to Broadway, as was the set in "Young Frankenstein". However, the inflatable set did not work for me.