Originally Posted by Wheel Experts

to sum it up, the reverse uses a true-to-size center that is "reverse dropped" which yields a straight flat lip. A reverse 19" wheel has a true 19" center, while a 19" standard has an 18" center with a 1/2" "step" all the way around, thus making the wheel appear smaller.

In reality, it's a matter of personal taste. Some like the classic step design, some prefer the reverse.