Seems like the large knife is the better tool if at the same weight it can outchop AND out slice.
Many people would agree with you on that. That is why many people advocate a large knife as an ideal survival tool, see posts by Ron Hood and Greg Davenport for example.
When considering the total range of tasks possible, the knife comes out ahead of the hatchet under most circumstances.
A hatchet is a much more specialized tool, optimized for chopping, the the poll can also serve as a hammer, just be careful not to deform the eye.
Only the best of the 10" class of knives will outchop a well sharpened GB hatchet, think ABS class bowies and the Swamp Rat Battle Rat, Ranger RD9, Busse Battle Mistress, etc.
More neuteral or handle heavy knives, such as the BK9 and Cold Steel Trailmaster will be futher behind.
Perhaps I should have defined the term "outclass" to be a large and significant difference, say 25-35% in performance.
This is all really dependant on the type and thickness of wood being chopped. ON really thick wood (Say anything over 8-10") the hatchet will readily outpace a large knife because of the increased penetration, as well as the hatchet generally being more fluid with less binding.
However, if you are chopping wood that large, you really want to be using a full size axe or a saw.
When you are tlaking about felling, bucking and moving wood that size, you are talking about a major job, not something you would be doing in a typical wilderness outing or a survival situation. Most shelters are built with much smaller wood, well under 4".
If you want to drag a 10" tree any distance you better have a team of strong men or horses as it will weigh several hundred pounds, depending on the type of wood and height of the tree of course.
A person may choose a hatchet simply because it is a legal tool to carry and a large knife may be considered a weapon. Thus, I can keep an axe in my car and a hatchet strapped to my pack without raising an eyebrow, but if I strapped a 10" knife to my pack on public land, I may wind up in the pokey.