RAT is generally what you use before 7 months out to see everything that is available for the time you want since, unlike the booking page, it allows you to see availability for non-owned resorts even though you have not reached your 7 month booking date. If you are trying to reserve an often difficult to get room at 7 months out and it is a few minutes before 8 a.m. on the day you can reserve, you should be using the booking page to set things up so you can reserve at exactly 8 a.m.
And just an aside since you are fairly new, RAT used to be named the Check Reservation Availabilty Page but Disney changed its name because members kept calling it by its acronym.