pros - Excellent Track
Loads of space for other atractions
Not baking hot
Indoor area to keep the buftys happy and refuge for the masses if it pisses it down.
Other car attractions of interest already onsite
No other show on at this time of year so would attract more interest compaired to being in the middle of summer.

Cons - Cold, Wet and miserable highly possible (some might say this is a good thing though)
Risk of snow = no track
Higher risk of low turn out due to weather
Time of the year when RS's tend to be in bits or in storage