It depends.
Are you going to chip up whole trees or just the brushy parts? I run a 200+ Bandit disc chipper. It makes small compact chips, and cuts up weedy and viney material. I use it on up to 6" hardwoods. For bigger stuff I use the Morbark 2400 drum chipper, a beast compared to the Bandit, and just built heavier, got a little 80 horse turbo diesel in it. It makes bigger chips but it'll eat up a 10"+ diameter tree, 17" capacity. Good for land and lot clearing. If the Morbark were to break down on such a job, I'd just chip up the smaller limbs with the Bandit and load the logs for firewood sales. If you have to go a significant distance to job sites and want to stay as streamlined as possible, get a big drum chipper with a grapple and a big chipper dump. Chip up everything. It depends on what you want to do. What do you want to do?