Been around a couple, sure wasn't impressed at all with any of them, sorry if this isn't what you want to hear. Before I'd even consider one of those smaller units, not sure how much you have to chip, but I'd go with a diesel powered disk chipper, smaller units used go on sales pretty cheaply compared to a new skid steer chipper. The huge benefit to a self contained unit is, then you can use the skid steer with a grapple to somewhat feed the chipper without having to do it by hand. Let me retype that again, use the skid steer with a grapple to do the bulk of the labor of handing the brush and limbs and I've fed a couple chippers exactly that way, the whole tossing the stuff in by hand is good for the first five minutes, but after that, its time to sit in a skid steer and use that or an excavator with a thumb to feed the chipper. Most diesel disk chippers have variable speed power feed linked to the engine speed, so once the engine lugs down, the feed rolls stop or slow way down so you don't kill off the engine. That feature alone is worth it, once you actually kill off the skid steer engine with one of those smaller attachments, life sort of sucks to say the least.
Now if they have improved the skid steer units over the years or those tiny tow behinds with the small gas engines, I don't know, but I do know from what I've seen or been around of them, I wasn't even remotely impressed.
I'd either buy a larger diesel unit or hire someone to chip my stuff for me. Just my two cents. Best of luck on whatever you decide to do, not sure if your in an area you can burn it, but if that's an option, bon fires are sure nice for the kids or grand kids later in the evening and are the cheapest method yet to get rid of any woody material.