There are a number of prior threads on just this issue.
I've a DR
chipper for a 3ph (as do a few others who visit this forum), on an
L3410 at 29.5 pto HP. It's a lot less expensive than the independently powered units (which have the same
chipper unit), and works fine on 3-3.5 inch stuff (hardwood or otherwise) but 4 inch is marginal (advertised yes, in reality - only softwoods - with hardwoods the tractor rpm doesn't slow, but the
chipper vibrates and makes such a racket that you'll think it's going to break). The unit and fly wheel are light, so you need HP on your pto to provide a smooth progression of cutting (folks with pto HP under 20 don't seem as happy with the unit). I've had no problem, aside from the size limitation being a bit less than advertised. Sharpen the cutting blade (only 1) every 10 hours or so (I got an extra blade, so a sharp one is always available) to preserve good, fast function and small chips.
Keep in mind it's a gravity feed, so it takes longer to feed things in by hand. That said, at the usual DR sale price and free shipping, the unit is ideal for small/medium tasks such as controlling the limbs trimmed from the many dozen of oaks and pines on my property, and grinding up the larger brush piles.