COD BO 3 or 4

I haven't actually played IW as of yet but from what I've heard, Black Ops 3 is better as compared to IW for a number of reasons:

Black Ops 3 has an interesting campaign. It's story is by far the best story ever written for a CoD game.
The futuristic technology and all that stuff actually works for Black Ops 3. Hell, it only makes the game even better and more enjoyable. Skills like Hacking into an enemy's turret and turning it on them or turning their robots or their exo suits against them are pretty cool if you ask me. And these skills mentioned are just a few if you ask me. Truth be told, there are a lot more of these skills available in your cybercores and you get to choose the ones you wanna use. Oh and just so you know, your Rig can allow you to run on walls too