I think many of us might choose the dungeon event where you get to choose to side with the Lizardmen or Dwarves to be your favorite. I know I really love getting it - the earlier the better.
So, who do you choose and why?
I take the Lizard guys every time because of their exploring skill which I think it vital in the early game. They can go up against any animal on the map, and, if you are lucky to get Animal Husbandry early on, you have a great chance of building that Grand Menagerie. Also, I find that when I use them to explore other dungeons I seem to get decent results - you gotta love those poisoned blades!
One consideration for me, though, is where the dungeon is - which units will get a terrain advantage as often the ones you side against will attack. But, I have found just as often they will move on and ignore you.
Pick your poison: Lizardmen or Dwarves.
One more thing: I still think there is a bug associated with upgrading whatever you choose if your race isn't Lizardfolk or Dwarves. My Lizardmen upgrade to my race's Rangers, but retain their Lizard race.
So, who do you choose and why?
I take the Lizard guys every time because of their exploring skill which I think it vital in the early game. They can go up against any animal on the map, and, if you are lucky to get Animal Husbandry early on, you have a great chance of building that Grand Menagerie. Also, I find that when I use them to explore other dungeons I seem to get decent results - you gotta love those poisoned blades!

One consideration for me, though, is where the dungeon is - which units will get a terrain advantage as often the ones you side against will attack. But, I have found just as often they will move on and ignore you.
Pick your poison: Lizardmen or Dwarves.
One more thing: I still think there is a bug associated with upgrading whatever you choose if your race isn't Lizardfolk or Dwarves. My Lizardmen upgrade to my race's Rangers, but retain their Lizard race.
