From the website:
British armoured regiments were delighted to receive the new American-made M3 Grant tank, which gave them a tank with a gun as good as those on the German panzers, with armour to match. Rushed into service to meet the urgent need for a heavy 75mm-armed tank it took the Germans by surprise. Its thick armour and powerful 75mm gun are superior to most of the German panzers.
Its only real downside is its height, which makes it a conspicuous target in the desert. The placement of the 75mm gun makes it difficult to conceal the tank in a hull-down position behind terrain. At Alam el Halfa, with time to prepare a static defence, the British were able to partly overcome these difficulties by carefully choosing the placement of each Grant.