So you want to start a New army? What rules do you wanna play with and why do you like these 3 choices.
, as i'm not the one who should tell you which (Pre-) Heresy Era Army you should play, as I for myself, am totally dedicated to the III. But just wait a bit on choosing a Primarch, as Mortarion is supposed to be the one to be released next.
_________________
...What about a Bastion made out of Guardsmen as some form of sick sarcasm?...Or a Fortress of Redemption made out of Dark Angels - Sky Serpent