SPG BRG was a guarantee of lowest best available rate—they only compared SPG-BAR v OTA-BAR as the booked rate was irrelevant in the comparison (in fact, for a long time one didn’t even need to book a reservation in order to submit a claim). LNF is a guarantee of lowest actual booked rate. Marriott guarantees the best available rate for the same roomtype, amenities and cancelation policy as the ones on the reservation. Individual experiences differ, but I had at the most a 50% success rate with SPG and now have ~70% success rate with LNF. But what bothered me the most with SPG was the long delays in getting a reply, the slopiness with which they approached claim proccessing and the great lengths staff went to deny a claim, often by just making completely bogus excuses.