I really enjoy the discussion between the WWII and M43 models as both are two of my favorite shapes, and both tend to straddle the line between utility and martial applications.
The WWII was at one time considered by Uncle Bill to be the finest combo of tool weapon in HI's line up. Now, the various models coming out of the shop these days may alter that statement, but the WWII is simply going to be a much better jack of all trades.
The WWII with its straighter handle, longer grip (allowing various ways to hold the knife), robust belly with wasp waist is probably going to handle better to a new khukuri user. It will handle as a better tool first and weapon second, in my opinion.
The M43 will probably outchop the WWII due to it's steep curve. While the WWII offers several different grips, the curry M43 really only gives you purchase for one hammer-style grip. So while you don't get the flexibility of different ways to hold the knife, the m43 is going to hit like a ton of bricks. The m43 was designed in such a way as to be a very useful tool but a formidable weapon as well. One swing with the '43 will prove this point. The curve literally drives the point of the blade deep into your target. Of course it slams the sweet spot home effectively when chopping wood, but point-first wound channel against an enemy shoulder during hand-to-hand combat cannot be overlooked as a function of the design.
So, in my personal opinion (which along with a couple dollars will get you a small coffee at Starbuck's), the WWII excels as a great all 'round outdoor tool while the M-43 is more of what one might consider "traditional" in shape, a more weapon oriented khuk...and IMHO sexier to look at.