Eagle, Those 2 are not in the same class. The Gravely will probably please you-The DR ........I doubt it. I'm not sure how you plan to use it but every DR I've seen has a small disc(=low performance) and dumps the chips under the machine--No directable discharge. If those are the size machines that interest you check out WoodPro (made for years in New Jersey) and Crary Bearcat chippers. I own a Wood Pro and it romps all over a DR. http://www.wikco.com/Woodpro.html
you might want to check with DR directly. They often have pretty decent deals on returns and refurbished machines. They have been a great company to deal with in my experince and stand behind their products 100%. They also have a website and often run seasonal clearance and free shipping specials.