I guess challenging other schools to death matches is out...
Besides, it's hard to get your mouth to move out of synch with the words as you issue the challenge and wave your arms around in a menacing manner.
Of course you have to finish the challenge with an insult and a goofy menancing laugh for effect, also out of synch with your mouth movements.
Amazing what one CAN learn from old Kung Fu movies...
Sparring works very well.
Fighting is not about who is right, it is about who is left.
A year from now, no one will remember who used what style, or what technique, only who prevailed.