I think they are both hard in different ways, op.79 #2 has a lot of inner voices cross rhythms and subtle things in it, it's considered to be an "easier" piece, I don'r know why. In contrast op.119 #4 is very direct and straightforward, so I think it's easier to interpret. It requires a more bravura approach, there's nothing subtle about it. Chops wise, it is the more difficult of the two, mainly because of the lyrical Ab section where the melody is in the middle of the accompaniment in the RH. That always drives me nuts!
They're both about the same; for me, the op.119 #4 is harder.