Well... I've only played up to Chapter 8 and haven't seen Arzodius, Yardeniox, or Xirenze yet (because of my progress or that I missed them).
Honestly, I like Groxts the best. He's a really fast red dragon with swords!
I like how when he learned about the death of Zarxof he got all uncomposed but when he battled the heroes he was all "I'm better than you humans" attitude.
(Also, I have two questions. 1. Why isn't FtD on the list? 2. I heard characters mention "High Dragons" in the campaign. What defines a High Dragon? Which dragons are High Dragons?)