You can easily say that there are two types of heavy tanks, one is the heavy tank which have high HP and the other one is the armor based heavy tank which has a strong armor. The difference between them it is not very big, the hp tank is made to take damage, the armor tank is pretty much the same when is not being targeted by a high penetrating type of ammo.

Usually, the heavy tanks are used in open battles and face the enemy face to face. They are usually accompanied by other tanks or by other heavy tanks. They are very effective in close combat, but if it looks that you are to be defeated and your tank destroyed, you better run and hide to save at least your ammo and gun, rather to lose all your tank. You can attack from behind later or you can work as a scout tank having a low hp.

City maps area pain in the ass for some players. The key when playing in such particular map is to try and look for the flanking points of the map and to stay away from the middle points where you can be easily attacked from sides. You will achieve this in time and with experience. You must make a good planning and to keep an eye on the map in order to make your way on it.