Disadvantages of the Merkava
In combat, the Merkava is the best tank in the world, bar none. It even has the capability to engage helicopters with its main gun for chrissakes.
But it's not a vehicle designed for deployability, or range. It's designed for the sole purpose of fighting in the territories around Israel.
It's too heavy, too slow, and doesn't get enough range out of a full tank of gas to be much use in lots of scenarios.
But for the purposes of the IDF, it's absolutely perfect.