IFV advantage over MBT
When you are in a passenger seat of the IFV you get a floating camera that clearly shows surrounding threats over most obstacles. You get a little dot crosshair you can use to spot enemies for your team using this clear overview of the battlefield. Engineers hiding behind low barriers or Recons running in to plant C4 are all exposed.
In the passenger 'seat' of the MBT, you can mostly see the tail light as you hang on. I understand the MBT is not a passenger vehicle, so it shouldn't be as protected or comfortable an experience, but the point is that there is an unnecessary disparity in the power of the passengers when they should just be tagging along.
It would both be more balanced and interesting to have the IFV passenger's view in first person. It would introduce an element of tension as everyone is staring each other in this small metal box hoping they get to the objective without exploding, and looking at the minimap to judge when to get out instead of popping out as soon as they see a threat from the floating camera view.
Consider the difference in the IFV and MBT if you have a gunner, a secondary gunner, and a passenger engineer ready to repair. In the IFV, for no particular reason, the third player can also act as a better threat spotter than the top gunner, but not in the MBT.
The MBT passenger can look around a bit from ground level, but is also exposed hanging onto the outside of the vehicle.
The vehicle experience would be also greatly enhanced if there were also a vehicle-only VoIP, or at least if the commrose was more responsive and had a 'bail out' command. I made a previous post on the commrose.