The advantage of the track, most of the time you will see the same corner 4 to 10 times.
On the road, it's a real pain to try and do the same corners over and over.
On the track, there is NO speed limit or external distractions like cagers.
On the road, it's darn near impossible to SAFELY and LEGALLY an corner close to the bike's limits on the street, not to mention you only get half the road. On the track you can run wide or run off.
Running OFF, don't know of a track that has a ditch by the track. On the road most do.
On the road, most have guardrails, telephone poles, mail boxes, and cars coming the OPPOSITE direction. So your doing 50, there doing 50 meeting the is like a wall at 100.
Can you learn to ride very well on the street, sure. How many have experienced riders who have training to explain to others what there doing wrong.
Drive sane on the road, let it hang out on the track.
One go down on the street for just plastic's can pay for several track days.
A ticket alone can pay for a track day at many places, don't forget insurance increase's.
I can not update this thread I started, but PainFullySlo just started another good thread.
Here are some others.. Helpful Links
Watch, Twist of the Wrist II.. Has some good stuff to think about.