There is something which Akamai does and CloudFlare doesn't want to (at the moment): pay big sums to those big ISPs which refuse to peer and want to sell very expensive direct connections.
Both services seem to be highly available and very fast from around the world. What does Akamai do here that's better?
To provide an example: transit to DTAG via GTT (CloudFlare) is always saturated at peak hours. So Akamai has a big advantage (direct connection) if you want to reach Deutsche Telekom customers.