Im not going to get technical but, i say run both. They are both good. I run and have both. I run the one that "feels" good to me on the track that race day.
As far as the Kyosho chassis stiffner....Didnt get alot of testing with it yet but on my small home track, im liking the way it feels/runs. You dont have to have your chassis much (if any different), ride height wise.
The main reason i kept my 02s, was i prefer the A-arms. Since the A-arms are out and on some of my 03s...im still keeping my 02s also.