The Magician :
[khukuri]
The things are insanely heavy and will wear you out chopping briars.
There are a lot of types of khukuris, yes some are very heavy, I think the largest ones go 8-9 lbs. However there are smaller models, the thinner and lighter ones work well on light brush. Check out posts by Tom Holt in the HI forum, specifically in reference to his 25" Kobra.
For berry bushes and the like, a very thin machete works best. I would look for something ~ 1/16" thick, with a comfortable amount of reach, the longest you can handle. Expect to modifify the edge profile to get optimal levels of performance.
If you want to cut the hardwood saplings, this isn't a great choice as it will bind far too much, and the edge will take damage if you hit a branch or knot. You can thicken it of course, but then you lose performance on the lighter brush.
The HI kobra would be a solid choice as well as the PM from Camillus, on the latter avoid any hard contacts with the tip, as it is very thin, use the thicker part of the blade to do any heavy cutting. These don't work as well on the lighter stuff as the thin machete, but handle the woody vegetation better, and stay sharp much longer.
Newt's blades are very solid choices as well. I don't find the pointy swells he sometimes uses functional (see AK for example), but some people prefer them. I would avoid the Ontario RTAK because of past experience with QC issues from Ontario, mine and friends.
The Martindale Jungle knife makes a very good tool for such work as well, just like the PM, avoid any heavy work near the tip. On the Jungle knife the edge is very acute there and you can ripple it easily. It isn't hard to alter the profile though, just increase the angle a little until it stops deforming.
I modified the Jungle knife I have in several ways to increase its abilities. I putting in a high relief near the base, adjusted the angle near the tip to allow light limbing, and sharpened the spine for very heavy work. It is now very versatile over a broad range of tasks :
http://www.physics.mun.ca/~sstamp/images/jungle_knife_mod.jpg
Barteaux makes a very solid machete that performs those tasks well also. Expect some edge work initially to get the blade up to full performance. The heavy duty models are a bit overkill for light brush, but will work well on hardwood saplings.
-Cliff