I just 'moved up' from a 1993 KDX 200 (one of two years with upside down forks) to a 1999 KTM 200 EXC. For someone your size and weight I think the KTM is a no-brainer. You'd 'outgrow' the KDX so fast, you'd be sorry you didn't pop for the KTM to begin with. Also, you might find the KDX underpowered for your 230 pounds.
We've got two very different types of riding here in New Mexico. First there is typical western desert type 'badlands' type terrain. It's relatively open, sandy, big hills, sand washes, scary single track on the edge of really stupid drop offs. Some of it is like miles of motocross track. The other is typical wooded mountain; tight, narrow, rocky etc. The KTM is superior in the desert stuff because of the chassis and handling. I can easily ride the KTM at speeds that were scary on the KDX.
The KDX felt noodly and hinged in the middle compared to the KTM. This would be even more of a problem with your size weight. You weigh 100 pounds more than me !!! You'll be flexing the frame and forks. Especially if you get air over jumps. I was having trouble bottoming out the KDX front end and I'm only 130 pounds. The KTM will save your 230 pound rear-end when you screw up. I've survived mistakes on the KTM where the KDX would have slammed me down. Like nailing the front end into dips or whoops. The KTM just soaked it up.
They 'bounce' differently. Get into trouble in the KDX and it goes sideways and all over the place and the front end wants to tuck under and slam you down. The KTM bounces too but it keeps going straight. Just stay on the gas and you'll survive 99% of those episodes. Even getting stupid and out of shape in whoops, just stay on the gas.
The KDX doesn't have anywhere near the precision and directional stability of the KTM. It's better in the woods. We've got some super narrow single track through the woods (like 10 inches wide, much narrower than a footpath). On the KDX, the front wheel was always trying crawl out of the groove. And I had trouble holding a line, like on those nasty rocky hills where there's only one good line, or you have to change sides half way up to avoid a killer rock or root. I thought it was my riding skills. Then I got on my friends KTM 200 and the problem vanished. The minute I got on the KTM I could ride it probably 25-30% faster than my KDX. It was such a revelation.
And I was instantly dissatisfied with the KDX. I knew that was going to happen, I went through the same thing 30 years ago. I was perfectly happy with my 1976 Bultaco Pursang 250, until I rode a friends KTM.
I haven't sold the KDX yet. I took it out a couple of weekends ago and rode it again for comparison. I was riding it SO much better, because the KTM has brought my skills and confidence way up.
-Joanne