Tough question!
In my opinion camera change can be harder to work with if this is a multiplayer platform. You gotta think about how other players will see you aiming. Will your fp char still be lifting his arms? If so it might be easier to just take the normal follow camera and parent it to the head socket where you would then tilt it a bit to adjust to the lifting of your weapon.
I feel like adding an extra camera gives me a hassle with each individual and unique weapon I use, on top of the weapon wobbling due to blendspace issues.
TLDR; Animation > Extra Camera!