Two Hawks :
Making a good axe that works is very different from making a good knife that works.
Steel alloys, edge grinds, and ergonomics (e.g., balance) are very different between "chopping knives" and axes/hawks.
I would agree with the above very strongly. However there is a big distinction between an axe and a hatchet, which is being discussed here. The impact energies of axes are easily 25+ times that of a hatchet. 'Hawks, because they have to be able to be thrown (more than once), are also in another durability class above hatchets.
The major knife manufacturers have a lot of experience in one area but it does not necessarily translate unless you have spent a lot of time on the engineering of dedicated chopping tools
Specific to Busse Combat (I have no experience with Greco, either the man or his blades), and Jerry Busse in particular, this is a topic which has commanded his attention for a significant amount of time. While I have *not* used the Busse Combat hatchet :
http://www.bussecombat.com/images/hatchet2.jpg
Based on the pictures I have seen of it, and my impression of Busse's dedication to functionality, I would bet that it is a very solid performer for its weight class 14 oz.
For example comparing it to the Gransfors Bruks Wildlife Hatchet I would expect the Busse Combat one to in general cut better (note the head design for a high grip) and hold an edge longer, and as well be more durable edge wise (steel and geometry issues). The Wildlife Hatchet should outchop it, however I don't think it would be a blow out because its greater mass (40% heavier) would be counteracted by the thinner bit on the Busse Combat Hatchet. The biggest difference would be in regards to splitting and chopping in soft woods where the heavy cheeks of the Wildlife Hatchet would prevent excessive binding. The Wildlife Hatchet also has a wider poll so it would be better at pounding stakes and such (the extra weight also coming into play here).
If someone has used the Busse Combat hatchet and the above is really off from how it actually performs I would be interested to hear about it.
-Cliff