The travel assistant can get Starchoice points and stayer can get SPG points if he/she is an SPG member.
It seems to me that Starchoice is available for only Asia/Pacific, Europe, Middle East/Africa region and to be a Starchoice member is required an invitation by Starwood employee.
Sometimes, Starchoice members can get special prices or benefits from the web site.
Since I became a Starchoice member, I am enjoying it together with SPG!