I've used Mazuri, Pretty Pets and Repcal.
I agree with another poster - they are all made from the same old pet food ingredients of convenience (corn, soy, oats, etc.) mashed together into an easy to serve item. Topped off with added vitamins and minerals to overcome the deficiencies of these ingredients.
Mazuri recommends feeding the item along with hay and grasses. also some fruits and vegetables can be added.
I've raised russians that are healthy and reproducing using little to no pelleted foods. I can get by without it. Right now I add RepCal to their diet about once a month after soaking it and rolling it in calcium powder. It's a convenient way to get the extra calcium into them.
I think I could cut back to once a century and they'd do just as well. They also nibble on cuttlebone.
My final evaluation (as I've said before): It's nothing special. If you've got a variety of weeds and grasses to feed your herbivorous tortoise - just keep doing that. It seems (I may be wrong) that most people who feed Mazuri use it far less than recommended by the company.