Yeah, teeth down in front, or teeth up in rear, increases torque/acceleration, at the cost of making it rev up to redline faster and having a lower top speed in each gear. I went down a tooth in the front and it picks up quicker. Instead of redlining in first gear at 86mph, it's more like 80mph now. Big deal. But the speedo still says 86 because it's calibrated for stock. Oh well makes me less likely to get a speeding ticket.
On a 600 I would go down a tooth in front and two up in the back. You can get decent Renthal sprockets for cheap that do the job, myself I wouldn't pay any more for something that won't do much better than that. 2 teeth in the back is worth 1 in the front.