Long Train Running is good also, but I do not remember if Doobies played that when I saw them in the Superdome with Van Halen and The Stones. Tickets for that were about $20, around 1979 or 1980.
Never saw Tull.
Edit: Just thought of one of the greatest train songs of all time.
I like both, but as a Jethro Tull fan and because of the piano intro, I have to choose 'Locomotive Breath'.
Other 'trains' I enjoy :~ 'If I Ever Get Lucky Mama (Win My Train Fare Home)' ~ Robert Plant 'This Train' ~ Sandy Denny (feat. Alex Campbell & Johnny Silvo) 'Doctor Zhivago's Train' ~ Robert Palmer