quanzhen sect-shaking treasure, the Chong Yang Sword + Heavenly Sword definitely make the 2 oldies more dangerous than they already are.
however in terms of raw power and speed, XF + DFBB holds the clear edge. i'm sure within the first 100 moves exchanged, both taoists will be surprised at the power and speed of their opponents.
for martial arts philosophies/knowledge and uber formations, Z3F + WCY holds a clear edge. you just know they gonna have these always-adapting, cosmic-related "owning" formations to use in this match up. to pull off a win, however, they're gonna need to utilize the philosophies "Soft overcomes Hards" and "Slow overcomes Fast" to the max before getting overwhelmed by the raw power of XF and the dazzling speed of DFBB.
i believe its doable though because both of em oldies are such superior martial artists.