I'll give a write up of this just incase anyone was thinking about buying it. First off i never played unity as the reports were horrible about glitching and the fact they gave season pass holders a free game as an apology is ubisofts admittance that they sent out shit. First impressions were great, it had the feel of AC2 which is what i expect as standard now, and the industrial revolution setting of london looks fantastic.
There are a few changes as there is no gameplay outside the animus, just video's, (at least up to chapter 5 where i am). You control 2 characters which can be switched any time via the pause menu.
The biggest diference is that they have tried to make it almost like an RPG only there is just 10 levels each, every 1000xp converts to 1 skill point but xp is shared so if 1 character gets to level 10 then the second will have the skill points to get there aswell. They can buy he same skills BUT Jacob is a fighter so he has special (Jacob only) perks whereas Evie is stealth based so she has certain perks only she can obtain.
Onto gameplay, story wise i have no idea what it is really as it has the chapter but it opens all memories at the same time so you can just do them in any order, also chapter 8 is open when you get to chapter 4 although i haven't done it yet. There is only 8 chapters instead of the usual 12-15 but they have thrown in extra "side quests" in the form of Darwin, Dickens, A G Bell and Jack the Ripper if you want to invest in the DLC (i didn't).
One massive downside (for me anyway) was the glitchy controls later on in the game, R2 & X will free run up buildings and R2 & O run down buildings, it al sounds great but if you are standing on the edge of the building and not running already you just try to climb down the wall which almost always lets the enemy escape.
All in all its a good game but it lacks the greatness that i got from AC2, Brotherhood & Black flag