You guys are missing one vital piece of the gearing calculations- the primary reduction. The primary reduction of the 450 is 2.818 and the 426 is 2.952. If you do the math, (if I remember right) the 450 is actually a little TALLER geared than the 426. So all things being equal, with both bikes at the same engine rpm, (and both bikes in their TOP gear) the 450 will have a slightly faster rear wheel speed.
You aren't remembering it correctly. With stock gearing the 426 is geared, overall, just slightly taller (about 3%) than a 450. That should change for the '05 model.
The 4 speed in the YZ450 is perfect for the bikes INTENDED USE. Remember it is a Motocross bike, not a trail bike. And also remember it's recommended for EXPERIENCED RIDERS, as per Yamaha's literature. That means if you're getting passed by a KDX200, you're probably on the wrong bike.
I believe the guy who posted about getting passed by a KDX was talking about top speed (on a road) so implying he can't ride is missing the point entirely, and not a very polite thing to do in any case.
Also, just because a certain feature suits your intended use doesn't mean it will work for everybody. Stating that the bike was INTENDED to be raced on a motocross track is just stating the obvious, by now everybody knows the YZ 450 has a four speed.