Both great bikes. The KTM's are perfect out of the box as far as springs for your weight. Jetting, just follow the recommendations in the Orange KTM manual for your elevation and temperature.
The only mods we do to our KTMs are bulletproofing, skidplates, hand guards, pipe protectors, shark fins,....
You will be amazed at the KTM200 performance, you'll wanna sell your KDX, too.
If I were your weight, and lived at low elevation, I'd ride a 200. As is, I am a fatboy living at 7,000' elevation, race as a 45 yr old A rider, and chose to ride 250's or 300's