Mary:

I will apologize in advance for doing this to you but...The rule is "The favored way up is the favored way down." Barring any tides and swell. If you just consider the wind and why it would be favored one way over the other it is because of a constant Arc of the Wind. Another rule (remember rules are not always fact) is that wind will hit land at 90 degrees. If there is wind angle of anything other than 90 degrees leading to a landmass out on the water the wind will bend toward 90 for that mass.

Here is an exaggerated illustration I made up of for sailing angles due to wind arc.



A spinnaker Catamaran, in moderate breeze, will sail 180 degree angles off the wind than it does toward the wind. Most other boats will depend on shortest distances as well and I think you can interpolate with this illustration if you sail lower angles.

You will sail shorter distances if you sail first to the center of the arc of the wind. This goes for both upwind and downwind. While going to weather you will notice a constant header on the first leg.

As mentioned before this does not consider tides, currents, or waves. This presumes you have constant wind speed and no wind line outside that effects pressure. "Pressure is King!" Your mileage may vary.

Later,
Dan