Which story arc do you like most from both series?? My favorite arc for Index in the anime has to the Academia City Invasion Arc where we first met Vento and Acqua as well as Terra brief appearance, triggering the event of Season 3 first arc... As for Railgun side, my Favorite arc is Sister Arc, as we get to see the same arc that was in index's novel been extended and was told from a different point of view, which I really enjoy it very much... Of course this isn't my favorite arc for the novel and manga, I mean its my favorite yes, but there also there other arcs that I really enjoy in the novel and manga... I will be added a new tread that contains the changes that was made to the anime. Which should be up in the next few days.