Halo 1:
Vehicles were invincible but could be toppled with grenades easily. This often caused them to crash and leave the driver vulnerable. At the same time though they had very good firepower. Losing a vehicle wasn’t the end of the world either, you could always fight to get it back due to them being invincible and never despawning, so neither drivers nor infantry were harshly punished.
The tank was the exception to the rule, but the driver was vulnerable through the cover of his seat, meaning you could snipe him out. Rockets and grenades were enough to take them out because they were all land based (except the banshee on the PC version).
Balance:
Weak but common.
Halo 2 and Halo 3:
Although vehicles were destructible they were still very durable. They couldn’t be toppled over as easily anymore, but this was replaced with the ability to board them and kick opponents out. Although the tank was no longer vulnerable to sniper fire you could still punch enemies out and take the tank for yourself at the cost of damaging the tank. Halo 2 had a homing rocket launcher and Halo 3 had a missile pod/spartan laser to make up for the addition of aircraft.
Balance:
Strong but not as common.
Halo 4:
Boarding and power weapons are no longer necessary to destroy vehicles. There is little to no strategy involved, you just spam firearms at them until they blow up or you use the plasma pistol and plasma grenades. Being in a vehicle is very short lived, there is little reward for actually acquiring one.
Balance:
Both weak and uncommon.