I had the 200 and now the 450. I loved the light weight and flickablity of the 200. The 200 made me a better rider because I had to be aggressive on it all of the time. It also took a toll on my already beaten and battered 34 year old body. I have since switched to the bigger and heavier 450 and find that it takes much less energy to ride and is much easier on the old body. I like to ride aggressively on tight single track trails and I don't miss the 200. I don't notice the extra weight of the 450, which is what I was afraid of, becasue it has so much low end power and is very easy to control. I've only road one 300 for a brief time and found it to have four stroke like power, but I am sure you would have to be more careful with the throttle than my 450. So what I'm saying here is that it is a late night, I couldn't sleep and all of this rambling is just a bunch of rambling and probably isn't helping one bit.
The only thing I can really tell you is that I didn't notice the extra weight of the bigger KTM near as much as I thought I would and I am only 150# and 5'8". After having the 200 for two years and loving the bike, I did find myself looking for a little more power. In all honesty though it will run right with a 250 for the most part. The only time you notice it lacking in the cc department is on narly hills and wide open top end areas.
I should also add that I owned a DRZ400 for a very brief time. It was the dirt only version, which I converted to dual sport. In my opinion it was a great dual sport bike, but compared to either of the KTM's that I have owned it felt clumsy and awkward in the woods. The components are also made a lot cheaper than the KTM. Everything from the seat cover and graphics all the way up to the handlebars and so on. I don't miss it one little bit (ok, maybe that cushy seat when I'm riding a long enduro).
Neal