I'm no expert but I've worked on a few and I've read quite a bit. :wink:
Different animals, that's for sure. As simple as they are they are deceptively complicated in the details.
Brilliant design really. Less weight, roughly twice the power and much cheaper to manufacture than a 4 stroke.
A person can rebuild one in 2 hours on the kitchen table for very little money.
The downsides of course are the smoke and the noise and the lousy range due to poor economy.
There's also the emissions concern for those who care about such things.
Personally if I found a good deal on a KDX I'd jump on it!