Well, for most of my Lego-ing career, I only had Crusaders, and in the past year or so I have had NO official factions, but in the time inbetween (say about a year or so), it was mostly a draw. But I've decided that if it happened now, it'd probably be the Black Falcons.
when Alex and I have a battle we usually roll a die to see who wins the little fights. if I am attacking and he is defending and I get the higher number his guy is doomed. If he gets the higher number he has successfully defended himself. then the defender gets to either attack or run away. whoever has the last guys standing wins the battle.
SO to answer your question - its totally random.
and in the end the loser gets eaten by orcs anyway.
I'll say Crusaders, but ony because they have that euro armor knight with horse barding in 6081. That is my second vavorite fig after the euro armored knight with white dragon plumes in 6086. I'm not sure why I'm making a decision based on one figure, though.
My falcons would probly win just because they out number my crusaders 3-1. Although after I score a complete king's castle off ebay, I'll be ready to challenge the legion of the black falcons again. Who knows. Maybe the Wolfpack will spring out of the shadows and slay everyone and turn there rag-tag gang into a well armed force and take over everything in medival legoland!
Why do you need all those minifigs? You'll poke your eye out!