Pro Open-world gameplay
Unlike the original game which was pretty linear, Catalyst allows for more of an open-world experience, so it is up to the user how they want to traverse the world when they need to accomplish a mission, which really frees people up to experiment and enjoy the free running aspect a lot more.
Con Gunplay removed
The original game had gunplay in it for combat, while not the best implementation it could have been expanded on. Catalyst has removed all gunplay to allow for hand to hand combat. So for those that did enjoy the gunplay in the original game, it will be completely absent in the new release.