Everyone has their own reasons for deciding on one army over another. Personally, I chose Menoth because I thought the Exemplar Bastions looked amazing. So I went and read each factions fluff in the MkII Rule Book, the idea of playing a certifiably insane bunch of fanatics was really appealing. There is no doubt in them, they are a single purpose bunch of crazies. Just my kind of army... (I play Orks in 40k if that tells you anything)
What I wanted to know was... what got you interested in your chosen faction? What made you want to play Cygnar or Trolls or Everblight? Did they look cool? Did their play style appeal to you? Or did you just throw a dart at the map?