I am not sure about the Coral Princess, but on the Grand and Golden a BF is a " balcony guarantee" . If you are not picky about your location, but definately want a balcony then this is the way to go. We booked a BF in Sept for our April cruise, then at the beginning of Jan. we noticed a price drop, so we had our ta contact Princess. We had the option of getting upgraded to a mini suite or saving 250.00 dollars.and still getting a upgrade to a BC. We chose the money. Then about a week ago we got our cabin assignment, we were upgraded to a Cat BA. So still 2 months to go and there is always the possiblitly of another upgrade, which would put us in a mini suite!!. We are very happy with the cabin we have now, ( a balcony on the Lido deck) so any thing more is just gravey!
Point is , IMHO is that a BF is a great way to book IF you do not mind where your cabin is located( we didn't) and there is always the chance of a upgrade!