Depends on your planned use of the car. I ran a delta fin in my car with great success on the road course, but it wasn't so good for the 1/4 mile.
Testing showed that the bar and plate is better for 1/4 mile runs as it can soak the heat up faster, but they tend not to release the heat as quick as the cooling air flow through them is less efficient because of the square edges.
The delta fin is better for long endurance so long as you have good air flow through them, because the cooling air is less turbulent so heat removal is more efficient, but if air flow is low then they heat soak quicker as they don't have the surface area as the same sized bar and plate.
Fraser