The RC-6 is a pretty decent chopper. Don't go by the specs. If you haven't had this knife in your hand then it is difficult to convince you that the blade actually has some good weight to it, mainly provided by its wideness (1.5" wide).
Okay, comparing it to a 9" blade, it is not going to win a chopping competition. Yet at the same time it is something that is fully serviceable chopping 3" to 4" trees. You won't have any problem doing this. Chopping larger pieces of wood really requires specialized instruments - but then why do you need to chop large pieces of wood? If I were to stack firewood for multiple days - yeah I'd go big. I'd also have a full on axe.
You can snap cut 1" limbs with single chops and it is highly effective at limbing pine bows for example. While some people think - not a great chopper, I tend to look at it in reverse. For its versatility of size and weight it is a great chopper. Basically, I'd say you can chop anything with an RC-6 as you could with a 9" knife, it just will take you a little longer to do it. On the other hand, this thing handles at fine cutting chores much better than a larger knife.
One of the greatest attributes of this knife is its balance. The claim on the RC-website holds true in this case. As mentioned above, I also find that it serves better to use more controlled and accurate hits rather than power swings. This is more effective and safe than chopping wildly.
Now yesterday I was chopping with a buddies Busse Sarsquatch. The Sarsquatch is a great chopper, no doubt about that. I still think my comment holds above though. I'm convinced the RC-6 will do anything (woods related) the Busse can do, it will just take more time to do it. Finally, putting a convex edge on mine did help significantly with the chopping!