The slightly older KTM 200's are very similar power-wise to the '03; the '03 got a revised frame and suspension and IMO it feels a little more nimble and better suspended. Nothing wrong with the older ones - I rode a 2000 a few times and loved it, just not as much as the '03. If the engine is tuned right, it will run pretty good regardless of year.
Kawasaki has hardly changed the KDX since '95, so one year should be as good as the other. The KDX is a great buy, but the power and suspension are not as aggressive as the KTM 200. It's a little heavier. Stock jetting and forks need work, but the fixes are known. If you are looking for the most bang for your buck in a woods bike, it is hard to argue with a KDX. You can probably find a decent one for $1,500 - $2,000. The 200 and 220 have different power characteristics.
Riding in the woods is my favorite type of riding, but everybody has different preferences for what type of bike is most fun. So try trading with with friends before buying. For me, 200-250 two strokes bring the most grins and are the least tiring, but there are plenty of guys who love the big 4 strokes. Good luck with finding the right bike for you!