The M-43 is one of my favorite khuks.
Generally speaking, the M-43 is going to come in just a tad thinner in the spine than a comparable AK. An 18" AK will probably measure around 1/2" at the base of the spine near the bolster while the M-43 might measure closer to 3/8".
As far as handling goes, the M-43 is a whole different animal compared to an AK. While the AK is a formidable weapon to be sure, it has more of a neutral "tool choppiness" to its swing...if that makes sense

The AK is a bit straighter in profile so it really allows you to chop with different parts of the blade a little easier. Also, the natural point of impact (POI) is right at the broadest part of the "sweet spot" (the hardest area of the blade edge starting usually about 2" from the tip and running back 4-6" toward the grip).
The M-43 is a very curvaceous khuk. From tip to buttcap, it is usually (more or less) one continuous angle. What this does is two things: First, the grip tends to be a little more singular in nature. Sure you can still choke up or down a bit, but not to the extent of an AK and certainly not as much as an 18" WWII. However, the grip angle really locks your hand in. There is no need for the grip rings that usually need to be altered a bit to fit the users individual hand. The second thing the angle does is make this a very tip heavy and give it a more "martial choppiness". The natural swing pattern tends to drive the straight down in an arch rather than a natural contact at the sweet spot.
You can certainly still chop acres of wood with the M-43. It'll do the job quite well

Just keep in mind that this is a representation of a khuk carried by the Gurkhas in WWII where the khuk was used not only as a tool, but as a fierce hand to hand combat blade. It needed to be functional enough to build a shelter, but it also had to have a natural POI that would offer a killing blow. I have no doubt in my mind that a quality M-43-like khuk in the hands of skilled Gurkha could have easily penetrated a steel helmet of the time.
We've all seen the trench spike of WWI trench warfare. Imagine what 2lbs of curved steel could do when it collided headlong into an enemy
Personally, I just really like the way the M-43 points. It chops well for me. I even used mine to cut the brush and wood my groomsmen and I used for our bonfire the night before my wedding. I keep mine by my bedside these days. Makes a great partner for Mr. .45 sleeping in the drawer. It even used to ride around as my truck khuk until I picked up a Boomerang AK a couple years ago. The Boomerang is a khuk that pops up on the Deal of the day sometimes. Think of a 15" version of a love child between an AK and an M-43. Chops well, comfy, and compact enough to just stash under the seat:thumbup:
Edit to add that MY version of the M-43 is quite a bit curvier than Nicolas' fine example

That's the beauty of HI khuks, you could get 20 of the "same" model and every one of them would be worlds of difference from the others....yet they'd all be good
