Transfer to airline points, get 25% bonus.
For example, if you transfer 20k SPG points to AA, you got 25k miles.
But that's the worst use of SPG points, best is points + cash, for example,
$40 + 4000 points for a $200 hotel.
Even if you don't stay in hotel that often, the one vacation you use it, it
will save you lots of money.