Based on pure stats the people have gone for the CT230R '08 event.
Does not pay the highest credits per min but pays the best EXP for leveling up the drivers.
Prizes CR Exact values
Prizes EXP( Formula based for info only +/- 300)
Which will then result in higher place finishes due to higher skill stats as you level up.
The Super car difference level will decide the winner you have very little controll over that as its still random selection of its driver. After the top 3 cars the pack is very even.