"much easier to work with" "easier to use"
"challenge, or the like"

I don't understand why 12-bar would be much easier to work with than 16-bar, for someone in about 1905-1911, because the chords in IV-IV-I-I-IV-IV-I-I consist of the same chords as in IV-IV-I-I, but twice, and musicians roughly Bechet's age were used to chord progressions that went ... X-X-Y-Y-X-X-Y-Y....