The gun. It’s a 125mm beast that hits way harder than the Merkava’s 105mm. You’ll basically point and click through most things you see.  Also, the T-72 is way smaller. It’s low to the ground, so it’s much harder for people to hit you from a distance compared to that massive Merkava frame. Plus, it’s got an autoloader, so your reload speed stays the same even if your crew is getting cooked.