speed difference between tacks

Originally posted by Jon Emmett If it was easier to keep the crew out on one tack than the other it may well be a pressure difference (sailing into/away from more wind). Tidal differences are still relatively gradual.

I'd agree with this - if you're sailing on a header you think there is enough wind to keep yourself out on the wire, but there isn't because you're always heading away from the pressure.  Sailing in a wind bend can have the same effect.  I am sure someone more scientific than me can explain it better.