It depends whether you are testing stamina or just those couple of minutes when one song lasts. Sondheim is very tricky, but other shows to require more stamina. SITPWG is vocally demanding, but not as physically demanding.
One good example of the challenge of Sondheim is a song which isn't on Broadway now, but was recently; Being Alive. It's only a top Ab at the end, but it's extremely hard to get that out cleanly after
acting the rest of the song, which does usually involve slightly shouty-groany bits which grate your vocal chords a lot.
The rain we knew is a thing of the past -
deep-delving, dark, deliberate you would say
browsing on spire and bogland; but today
our sky-blue slates are steaming in the sun,
our yachts tinkling and dancing in the bay
like racehorses. We contemplate at last
shining windows, a future forbidden to no one.
Derek Mahon
"Maybe all one can do is hope to end up with the right regrets."
Arthur Miller