I don't believe the OP is asking about transferring MR points to Starpoints. Rather, he is talking about this program, which allows Membership Rewards earners to book whatever hotel (or other travel) they wish, whether it is affiliated with SPG or not. Regardless, using SPG points still seems to have the best value for the OP's situation in any case.

I miss the days when there were occasional transfer promos when MR could be converted to SPG at 2:1. It seems like it's been many years since that's been offered.