Go for the carbon F2c. I own a '05 limited edition F3c which is the exact bike as the '05 F2c except for different decals. I love it !! It's a great ride. Completed (6) century's this year and I felt great coming off the bike. It's smooth down the road and climbs like a goat. Don't know much about the scandium F15 but I can't imagine it's near the carbon frame ride that the F2c would be.

Bikegerm