I am buying a ticket to Asia soon. I fly often Air Canada which is affiliated with StarAlliance and manage to collect some aeroplan points and I've already redeemed 3 domestic flights. It will save me $175 less to fly with Northwest (w/ Sky Alliance) where I don't have an account with. However I do have some airmiles when shopping at Safeway and taking the odd flight on WestJet. Save money or Spend more for the points??