I want to run the knights and firelance. I know it's not good but I just enjoy playing it. Plus we have some new guys joining the group and figure I'd run some weaker lists. I was wondering if people preferred the Carnosaur or the Cold One for the battalion?
Both. I prefer the ScarVet on Cold One as General and part of the Firelance, but also put a Carnosaur on the list. It takes away a bit of fire that would otherwise hit the General and his Starhost.
Cold one is a better commander, especially for a firelance starhost, as his command ability is just better especially when taking into account it affects all saurus near him not just the one unit. Carnosaur is a better fighter, but also has a giant bullseye painted on his face... As @Aginor says combining the two might be best. Cold one sticks with the Knights to command, Carnosaur goes off to eat some stuff and pull away some fire.