Starwood has always had one of the best loyalty programs out there. The hotel company has partnered with over 30 airlines to give really great points transfers to many of those airlines. Almost all airline partners have a 1:1 point transfer rate, nothing quite beats the 1:1 transfer rate when it comes to points and miles.
Up until the merger with Marriott though, Starwood did not have a good transfer rate to United. Transferring to United came at a soul crushing 2 Starpoints to 1 United mile. When almost every airline that Starwood partnered with was offering a 1:1 transfer rate, the idea of transferring to United was terrible, you'd have to spend twice as many points to get the same number of miles that a rival airline would give you.
Now that has changed with the linking of accounts between Marriott and Starwood since Marriott has a very good partnership with United.
Using Marriott points, you can convert 112,000 Marriott Rewards points to 50,000 United miles, this is quite good for Marriott hotel rewards. However, when you look at the SPG points to Marriott rewards points conversion, things look even better.
SPG points now convert to Marriott rewards points at a 1:3 ratio, for every 1 Starpoint you transfer, you get 3 Marriott Rewards points. That means for 37334 Starpoints, you can transfer those to Marriott Rewards points and then to United MilagePlus miles. So for 37,334 Starpoints, you get 50,000 United miles! That's better than the 1:1 ratio that is offered by SPG to most other airlines, even when you factor in the free 5,000 miles SPG gives for every 25,000 points transferred.
This is the best way to use your Starwood points toward United. It might very well be one of the best redemptions possible on SPG all together now. If you have a trip you are planning on united, this may be a great way to boost your miles.