I am a 220lb woods rider. In 1999 I made the exact same switch that you are contemplating. I went from a '98 XR400 to a new '99 KTM 300EXC. I was kind of sceptical about going back to a 2-stroke but I have never regretted that move for even 1 second. The big surprise was that the KTM had almost as much bottom end as the thumper, which was one of the things that I was most worried about. Being 50 lbs lighter, easier to start when dropped and in the winter, electric like power delivery with no big hit and way more power on top than the XR were all double bonuses. Over the 3 years that I have owned it I like it better and better. The quality of the components is exceptional. After three years of trail riding 30 - 50 miles a week my compression is still 175-180, on the original top end. Jetting is very important on these bikes. After fooling with pilot and main jet changes, which did help I got the most dramatic improvement from going to a #7 slide. After getting a new bike every couple years I have decided to maintain this one and keep it as long as possible.
Other than the forks I don't know the specific comparisons about the '99, '00, '01 and '02. When I notice one on a ride I ask the owner to compare them if they previously owned a KTM. Nobody has mentioned any dramatic changes other than the forks, which do seem to provide a better ride.
Good luck with your decision.