Greetings! Sorry for the late reply.
I chose the Chthonic Lizard as a personal preference, mainly because of the +health and +willpower bonuses it provides. Since we use a lot of Reg./hit, we don't care about the -regen time to Capricious Hunter aspect. Also, if I'm not mistaken, the Capricious Hunter focused lizard doesn't provide the +willpower boost.
But in fact, you can basically choose whatever mount type you'd like, there's no cons if you choose, let's say, the CH focused one. The build will still work wonders no matter the mount
Hope I could help a little bit.