Well, I just got back in from clearing out heavy brush, saplings, and snags, from an acre on the back of the property that had become inaccessable. The tool I used was the Cold Steel Two-Hand Machete, and I'm now wondering how I ever got by without one. It takes care of everything from vines to 4" thick trees, bridging the gaps between a machete, a hachet, and a light ax. The steel is admittedly very soft (CS says 1050) and the edge it came with wasn't so good, but 15 minutes on a bench stone put a good utility edge on it. After clearing an acre of brush and small trees it could keep going, but I'm going to resharpen it. Using two hands really does make the job go much faster and lets you tackle bigger stuff than you'd normally use a machete for while still doing a good job on brush. I should note that the trees I was dealing with were alder and fir, not hardwoods. As a survival tool, this would be one great tool that could chop wood, blaze a trail, and could even serve as a defensive weapon. I've never seen anything quite so versatile, except perhaps a kukri (but you have to pay a lot more than $18 for a good kukri). Here's a link to CS's website on the Two-Handed Machete:
http://www.coldsteel.com/97thm.html
http://www.coldsteel.com/97thm.html