The historical progression:
Back in 1962, my late father, Forrest Bailey Johns, already a master gardener, retired from Shell Oil Company, and moved from Decatur, Illinois to Poplar Bluff, Missouri (His home state) and set up a serious garden. He had fruit trees, raspberries, logan berries, flowers, and his true love, tomatoes, in great quantitiy. One of the first equipment purchases he made was a WW Grinder. In those days, (almost 50 years ago) there were really no other substantial equipment alternatives available for the purpose of grinding compost.
A hobby gardener myself, and always in competition with my dad for the best tasting tomato, I purchased my WW Grinder in 1972. The best picture I can find:
I used that grinder for years, but it would not chip logs and had trouble handling wet product.
Around 1993, I bought a "commercial" chipper grinder from Norther Hydraulics. It came with an 8 horsepower engine and a direct drive to a flywheel that had two knives. It did an ok job but would not stand up to heavy use, and I completely wore it out in about 5 years.
Finally, in 1999, I bought a McKissic Mighty Mac 10 hp chipper/shredder. The cost was $1,350. I will say this: This shredder/chipper is good. It is the best I have ever used. It will easily chip up to 3 1/5 inch logs and rarely clogs, even with green material. One thing I would caution about. There were two oil fill plugs. I only noticed one. Last summer, while using the chipper, the "hidden" oil filler cap popped off and resulted in a blow out of oil and the destruction of the engine. I replaced the engine with an 11 hp Briggs (Cost only $374), which is a physically much larger engine, and required me to do a little mechanical engineering to make it fit. Specifically, I had to extend the mounting brackets and install a longer belt. BTW, this 11 HP engine ROCKS! While the original engine, a 10hp Briggs, was entirely sufficent, and would have lasted many years longer had I paid attention to the oil filler caps (Both of them) this new engine has HUGE power and I expect this will be the last chipper grinder I will ever need.
To be fair, I note that DR now has models that are comparable and even larger that were not available when I purchased my Merry Mac that appear to be very good machines that you might want to investigate.
Here is a picture of my modified Merry Mac. The plywood hopper addition facilitates the feeding of bags of leaves without having to hold the bag up.