There should be more tank statistics when you examine a tank and look at its health, damage, etc. There are much more things to the tank that actually affect the tank's performance, and they are mentioned in the upgrades section. Here are some I can think of right now:
- Accuracy (with each available ammo type)
- Reverse speed
- Clip reload (for the tanks that have clips or magazines)
- Front armor, hull armor, rear armor, turret armor
- Gun depression/elevation
And then there is aim down sights, but that isn't implemented.