Need a bit more info... What is the car going to be used for? How wide are the wheels? Are they going to be driven on the street regularly?
The RS3's aren't great when cold. Living up where you are, I'd suspect you could only really get them good and sticky 3-4 months a year. The Star specs are far less temp sensitive, and better in the wet. If these are on a street car, Star Specs all the way.
Don't get too concerned with 10mm. I suspect you're mounting on a 17x9 wheel? Any tire wider than 9" isn't going to be able to fully utilize the extra width anyways, and it will create a lot more heat fade on the track. Track tires stuffed on narrower wheels don't have to worry about this as much, because they can deal with the heat a lot better.
I'd worry more about getting one that keeps the overall diameter closest to the gearing you need for the track. Smaller diameter means lower top speed but better acceleration. Good for smaller tracks, can be a pain in the butt on the big ones.
2008 Bullitt - On Deck for Track Duty
1997 Cobra - SOLD