Winds on the Calif coast favor the north-south route pretty consistently. They can be very strong, 40+ mph.

IMO and experience, winds are more likely to be favorable if crossing the country west to east, especially in the mid west and west. OTOH, many prefer a east to west crossing to avoid the morning sun, as most riding seems to take place before late afternoon. There is a safety element in this, the rising sun blinding motorist. East to west also saves the best part for last from a scenery perspective.