Once you figure out how spg brg system works you will find it's amazing. You get to beat spgs absolute lowest rate, even if the rate is non cancellable. The only thing you have to book is a flexible stay and search around for a rate better than Spg's absolute lowest rate.
The brg system from Spg is so addicting that Marriott's feels way old school. Spg's partner Hotels however is a complete matter and utter nightmare lol.