after watching friends use smaller stand alone units, i got a tractor mounted chipper.
I thought about size, but with 60hp at the PTO, i went with an 8". i rarely put anything that big in, but bent pieces, lots of limbs, crooked y's and all the sorts don't have to be trimmed down. I got a Woodland Mills WC88. Hydraulic feed. It'll run me off my feet. With a helper it runs us both.
Just did a job the other day, i bet it would have taken 2 tandem dump truck loads to get rid of the tree tops and limbs from a land clearing. I chipped it all in 4 hours. the chips would have went in my 6x10 dump trailer if the owner wanted them cleaned up. some of it was approaching 6-8" but it was all poplar and balsam. quicker to make chips than cut firewood from these limbs. The machine burns 2-4L/hr (1/2-1gal/hr) of fuel, i too was wondering about the hours but really, it's so fast to chip compared to a smaller stand alone unit, and what the heck, it's kinda fun watching a 25' long Balsam with all the limbs on go through!!!
There's no way this crap coulda been burnt till November around here, or at $400 a dump truck load to haul it to the dump..... cheaper to chip too.