The statement "A modern concert featuring a single Romantic symphony would probably be longer than one featuring a Classical symphony. " is TRUE.
Music in the Classical era tends to consist also of shorter movements, because composers were still learning ways to extend their pieces. That is why Beethoven's "Eroica" is considered so ground breaking, because here is a symphony that lasts around 50 + minutes - twice the length of a symphony by Mozart or Haydn.
