One can convert Harrahs points to Hawaiian Airlines points, but it is at a low rate that I never considered. But you might do it if you are not returning to Vegas and the points would otherwise expire from inactivity (Harrahs points expire after one year of inactivity)

One can also get SPG points from the Westin slot card at a really good rate: 1 cent cashback gets one SPG point. However, it is more difficult to get points cheaply on the card since they lowered the points earning rate by 75% on their Shufflemaster blackjack machine. They have 25 cent progressive video poker that becomes positive expectancy on occasion; check the meters. I believe that the points accumulate on most machines at a 0.5% rate.