User blog comment:Master Sima Yi/Assassinews 12-05-'15 — Assassin's Creed: Syndicate has been revealed!/@comment-86.61.3.209-20150806200331/@comment-13471981-20150806201038

Quick summary: Storyline missions are assigned to either Jacob and Evie, you cannot choose. Jacob is said (but this has not been confirmed by Ubisoft I believe) to have more missions than Evie. However, in the open world you can freely switch between the both of them, so if you want to play all the side missions as Evie, you can. Not sure if there are character-specific side quest.

Jacob is a brawler, yes, while Evie is a stealth person - several of Evie's skills that you can unlock include being able to carry more throwing knives than her brother and being able to throw them farther, possessing 'voltaic bombs' (basically stun grenades that zap enemies with electricity) and being able to blend anywhere as long as she stays completely still (indicated visually by her going invisible - guards will most likely spot her if they get too close or hit her though). No confirmation on Jacob's exclusive skills yet, though he does have a Kukri knife (a kind of machete) that Evie doesn't seem to have.