Starwood Preferred Guest and Southwest Airlines are now official partners for points-to-miles transfers. The exchange rate is 1,500 Starpoints = 1 Southwest Rapid Rewards credit.
The 5,000 points bonus for a 20,000 points transfer earns 16.5 Rapid Rewards credits although the exchange rate is slightly better if you transfer 21,000 points to earn 17.5 credits with the bonus.
Earn 0.5 Rapid Rewards credits per stay with Airline Direct Deposit
You can also earn 0.5 credits per hotel stay at Starwood Hotels. This option requires airline direct deposit with SPG.
Earning points may be the better option in general since 21,000 points earns 17.5 credits or a rate of 1 Rapid rewards credit for 1,200 Starpoints. You will get better value taking points unless you anticipate earning fewer than 600 Starpoints for your stay.
Switching back and forth between earning points or SPG Airline Direct Deposit is possible, but inconvenient.
Four Points Hotels promotion earns 1 Rapid Rewards Credit per stay between August 18 and September 30.
For the next six weeks you may want Airline Direct Deposit to earn double Rapid Rewards credit for every Four Points hotel stay.