Burnham, Cooper and Kendall were all bland and indistinguishable from each other. All of them spoke in empty phrases (growing economy, fairer society etc...). All of them seemed to support blair-style new Labour. Corbyn was the only one to say anything substantial and also got few ovations from the audience. But even he didn't seem to believe that he could actually win the nomination. He was also the only one who was in favor immigration while the others tried to portray themselves as opposing it (although not very convincingly).
If I should bet who would become next Labour leader, I would guess Burnham.