I do not own one nor have I operated one.
However, this unit was made for Ingersoll by McKissic...one of the most respected names in the chipper/shredder industry. I have read numerous posts by those who do own one and everyone has raved about them. I have yet to read anything negative.
The chipper opening is three inches square and that should tell you something as far as how large a branch it can handle. But let's face some facts about wood in general. You have hardwoods and softwoods as well as fresh cut vs old dead wood. It should be obvious that hardwoods and dead wood will tougher to chip than softwoods and fresh cut. Also, branches have branches and those can get in the way when feeding any size of chipper made. This is not a unit that someone in the tree business is going to buy. It is intended for the homeowner that has a well-tree'd property and cannot burn the stuff he has to clean up in spring, fall and after a bad windstorm. It sits in the corner of his shed, quietly waiting for it to be needed once again. You don't have to spend time and money running to the rental store to spend more money to rent a chipper that is essentially too big for what you want to do and then spend more money and time to return it after filling up the gas tank on that chipper once again.
If you need a tool like this, then just go and buy it. Renting is a sucker's game unless you just need an item ONCE and I don't mean once a year. Of course, you have to service your Ingy chipper periodically and keep the blades sharp. They hold their resale value very well. In my opinion, any branch that will not fit into the Ingy chipper is called firewood..........either for you or for a neighbour.