Unless you are making deep dish, where sliced is the customary version, you will get a more consistant product by measuring shredded or diced cheese. Review the archives for this subject, and for Big Dave’s Cheese Cup procedure.
As to the question of shredding yourself or purchasing preshredded cheese, that depends on your staffing system and the cheese types available. If you have staff on hand that has the free time to grate cheese (ie. if you can lean, you can grate), then its more cost efficient to use the labor your already paying for, and purchase the cheese at the lowest possible cost…by the brick.
But if you are so busy that you would have to add staffing hours just to grate cheese, then its more efficient to purchase pregrated, or prediced.
As for the quesion of grated or diced… Grated works well if you measure cheese by weight, but can be inconsistant if you measure with cups. Especially if you grate yourself, as it tends to clump back together. Diced works well if you measure using cups and measure by weight, but isn’t available in every cheese brand.
Finally, consider your alternate cheese uses. Pregrated and prediced cheese are coated with a wax to prevent clumping. Thats great for pizzas, but not so great for salads. Also, you may not consider diced suitable for salad use.
Nick, I used an 11 quart Kitchen Aid for 4 years. For 300#s per week, you will use about 4 $55 blade kits per year, but the kitchen aid will endure just fine. It takes about 20 minutes to grate a tub containing 24#s of cheese. It was a fine system for sales under $5000 per week, but I have now switched to prediced, so I could use my labor on other prep.