The 600-class sportbikes will dominate on most tracks; especially if the rider is good. You have to spin the smaller engine, though they do make impressive power. The biggest advantage the 600's have is they can carry more speed through the turns. If they are on top of their game, you'll have a heck of a hard time making up the time in the straights.
If this is your first track day, DO NOT be concerned with going fast! This is a sure path to wadding up your bike and possibly getting hurt.
Concentrate on finding and following the proper line through the turns.
Concentrate on being smooth:
- smooth on throttle control
- smooth on & off the brakes
- smooth on your body positioning
- smooth in transitioning into & out of turns
If you are not smooth, fast will never come.
If it feels like you are going FAST and just about to crash, you are about to crash! ...yet you're not actually going that fast; you're just off the line and in trouble.
Slow is smooth, and smooth is fast.
Said another way:
Go slow enough to learn smooth... over time smooth becomes very fast.
If this isn't your first track day, then you already know all this stuff