^^I mostly agree. I started on dirt when I was 5...and started racing shortly after. As Jon said..it was an easy transition to street, and some skills from the dirt proved invaluable on the street. Skills guys who start on the street don't get.
I'll disagree a bit on the 600's. They are far from "hair trigger". Fast..heck yea! But their lack of torque and sky high RPM powerbands don't lend for the gob-smacking power that a liter bike (or open class bike) has. YOu have to rev the

out of those 600s to make them go. R6 had a near 17,000 RPM limit!
For the street I much prefer a twin (of almost any size), a single, and if a 4 banger...a liter class and up bike..
Oh...and here's a pic of the first corner carnage from this weekends race:
