I think Pulisic is miles better than Iwobi, its almost disrespectful to compare them. Iwobi has good close control but dogshit poor shooting and passing technique. 5 - 10 yard passes, he is fine. He has decent pace and strength too.
Pulisic has better close control, is completely 2 footed and has much better technique and is also pacy. Might be a tad lightweight but he seems to cope ok with it so far. Just my $0.02.
I cannot think of a single thing Iwobi is better than Pulisic at.