The ascendant is usually more important as the sign on the ascendant determines a person's chart ruler. The chart ruler, and any co-rulers, represent the person the chart is cast for.There are some exceptions to this. If the ascendant is Leo or Leo is intercepted in the first, then the sun sign is extremely important. In those cases, the sun would be the person's chart ruler or co-ruler. The sun can also have extra significance if the sun is part of a stellium or is in conjunction with the person's chart ruler.