User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-69.180.107.74-20150221165408/@comment-16281343-20150221171014

EPs are based on chess, that's why the concept of promotion is there.

BSs are based on cards/card games and the concept of promotion isn't a part of it. What's there is the possibility of cooperating with other Brave Saints to perform more powerful attacks. These combinations are based on existing card games (Royal Flush, Straight Flush, etc)

~With regards to their ranking, comparing Griselda's position to Irina's, then that would mean that Qs outrank As. So, it is the same with how EPs are ranked (Qs outrank Ps).