AC has 100% completion? Or are you talking about just doing all of the investigations? The concept of 100% sync as such wasn't introduced to the franchise until AC:B.
The gameplay in AC4 is smoother than any of the others. There's not as many annoying loading times as in other games. Transition from ship to shore and place to place is seamless. The fighting mechanism's pretty much the same as in AC3, though firing the multiple pistols makes it a little different. And this game has free-aim, which is also different. I suck at free-aim, so that's a bit challenging for me.
Edward is completely loyal to those he calls friends. I'm not far into the game, but the only woman he's been private with has been his wife, Caroline, who's back in England, waiting for me (flashbacks). Whether or not he indulges in the "Bettys" available in every port hasn't been touched on. But, then, even Ezio wasn't a complete cad, so we'll see. I like that he's got a sense of humor, has a fun wit, and doesn't back down from a challenge, yet he's not stupid. So far as I can tell, he's aware of his limitations, but will stretch himself when called upon. Money is important, yeah, but he's not a mindless mercenary. He wants a lot of money so he can give his wife finer things and not be a peasant all their lives, so his desire for money isn't straight greed.
