What size tires are best?

[Cole]

What size tires are best for MX racing? I have to admit, I like the look of the smaller tires the most. It seems the lower the bike is to the ground,the better it would be. Taller or shorter, which is best, and why?

Thanks

[QuadTrix6]

i like 19's bc of the handling and it lowers the bike and the 18's in the rear for the same reason