Billy,
If you haven't already purchased an Assassins Creed game and didn't play the PS3 series of games, then I suggest you go with Unity. It has a very neat cooperative game play feature that is new to the series. Also, if you haven't already purchased one, I suggest you look getting a headset. I personally use the Playstation Pulse Elite headset and it is fantastic, and comparatively not too expensive at $150. There is also the slightly cheaper version of this headset. It's the Playstation wireless stereo headset, it runs $100. Both of these are completly wireless (there is an even cheaper version, but it is a wired headset). I've owned the super expensive ($300) Astro A50 wireless surround headset and the Playstation wireless headsets are, IMO, just as good and half (or less) of the price. The other option would be to purchase the PS4 camera ($60 I think), it also has a mic and does a fairly good job of recoginizing your voice and eliminating the tv sound from the transmission.