F - e gives F+ and I - e gives I+ which reaction is more feasible?

In short I - e ---> l⁺ is more feasible.

The reason is as we move down the grp the distance of the Valence electrons from the nucleus increases hence ionisation potential decreases. So it's easy to take out an e^- from any element down the grp . Same goes here too l is placed down the grp so it easily looses an e^- from the valence shell making the reacⁿ more fessible.