There are significant differences in the quality of materials and workmanship that go into making these machines. They all look good when freshly painted; it is not always possible to know what you have bought until a season or two of heavy use has passed. One tried-and-true aid to choosing quality is to ask equipment rental businesses what brand their customers are not able to destroy. Another guide is to observe the brand of gasoline engine attached.
In my gardening career I've owned quite a few gas-powered rotary tillers and lawnmowers and one eight-horsepower shredder. In my experience there are two grades of small gasoline engines--"consumer" and the genuine "industrial." Like all consumer merchandise, consumer-grade engines are intended to be consumed. They have a design life of a few hundred hours and then are worn out. Most parts are made of soft, easily-machined aluminum, reinforced with small amounts of steel in vital places.
There are two genuinely superior American companies--Kohler and Wisconsin-that make very durable, long-lasting gas engines commonly found on small industrial equipment. With proper maintenance their machines are designed to endure thousands of hours of continuous use. I believe small gas engines made by Yamaha, Kawasaki, and especially Honda, are of equal or greater quality to anything made in America. I suggest you could do worse than to judge how long the maker expects their shredder/chipper to last by the motor it selects.
Gasoline-powered shredder/chippers cost from $700 to $1,300. Back in the early 1970s I wore one pretty well out in only one year of making fast compost for a half-acre Biodynamic French intensive market garden. When I amortized the cost of the machine into the value of both the compost and the vegetables I grew with the compost, and considered the amount of time I spent running the grinder against the extra energy it takes to turn ordinary slow compost heaps I decided I would be better off allowing my heaps to take more time to mature.
Sheet Composting
Decomposition happens rapidly in a hot compost heap with the main agents of decay being heat-loving microorganisms. Decomposition happens slowly at the soil's surface with the main agents of decay being soil animals. However, if the leaves and forest duff on the floor of a forest or a thick matted sod are tilled into the topsoil, decomposition is greatly accelerated.
For two centuries, frontier American agriculture depended on just such a method. Early pioneers would move into an untouched region, clear the forest, and plow in millennia of accumulated nutrients held as biomass on the forest floor. For a few years, perhaps a decade, or even twenty years if the soil carried a higher level of mineralization than the average, crops from forest soils grew magnificently. Then, unless other methods were introduced to rebuild fertility, yields, crop, animal, and human health all declined. When the less-leached grassy prairies of what we now call the Midwest were reached, even greater bounties were mined out for more years because rich black-soil grasslands contain more mineral nutrients and sod accumulates far more humus than do forests.
Sheet composting mimics this system while saving a great deal of effort. Instead of first heaping organic matter up, turning it several times, carting humus back to the garden, spreading it, and tilling it in, sheet composting conducts the decomposition process with far less effort right in the soil needing enrichment.
