Basically, I've just started my IG Army and am having trouble choosing which Cannon to put on my tank, For those of you not familiar with the options, they are as follows: Battle Cannon Vanquisher Battle Cannon Eradicator Nova Cannon Exterminator AutoCannon Any suggestion and why? Thanks!

as you can guess from the title. I haven't played in about 15 years and have just decided to get back into it with a guard army. Will start off small. I know the new codex is coming but i want to get a feel for it now. here are two lists i have come up with so far. Manpower based list command...