Originally Posted by phunk

18s will give you better grip.

wheel diameter does not effect surface area on the ground, that is tire diameter.

smaller wheels give you more sidewall, and more sidewall gives you more grip. This is because it allows the tire more compliance. More sidewall also increases drivetrain cushioning, softening the blow to things like your axles.

The advantage 19" has over 18" is less/stiffer sidewalls and less compliance. This is ideal for responsive handling, but the opposite of what is ideal for drag racing. 19" is going to hook up worse and be more likely to break your axles... but it will feel more sporty and confident in the turns.