A huge difference is that Jackson has always had better peripherals than his ERA, while Lannan has always had a much better ERA than his K rate, walk rate, WHIP, HR/FB, velocity, etc... would suggest. Lannan was always the guy the stat geeks would say was a mirage, while Jackson was always their superstar camouflaged by his ERA.
he's actually at a wierd point where his era and xfip are perfectly matched at 3.38- I don't think I've ever seen that before
