I've seen plenty of both Hannibal and Iqbal in the U18's / U21's, and for me Hannibal has the much higher ceiling of the two.
He has good technical ability and mobility, and can get up and down the pitch well and contribute on the ball and off it. His major weakness is his temperament, and learning how to keep that in check and to use his fieriness as a positive than a weakness.
Zidane isn't anywhere near as fiery - though you do need a good amount of that steel and desire at a young age to push yourself and improve, so which you'd prefer, and is easier to hone as they mature, is open to debate. Both are 'pretty' on the ball - with decent amount of touch, technique and vision. But I feel Iqbal plays at a much slower pace, and wants a lot of time on the ball and is limited in terms of having the ability to drive forward and hurt teams individually. Which Hannibal possesses.
That's why I feel Hannibal has the higher ceiling. I think he has the better all round midfield game and more potential, and that it's easier to hone his temperament than it is to improve Iqbal's pace, mobility, drive, etc.