I started with the space marines. It gives you a good foundation of game mechanics. Also when painting This gives you the option of making chaos warriors out of spare parts and that's like getting 2 for 1.
Oh hello (:
I would think dreadnought are deployed when resources are scarce and enemy deployment a pears manageable. This way the asset is not in extreme danger of loss but can be utilized to their full potential either strategically or managerially. Such as clean up after a major campaign when securing the location is of extreme importance but the major focus of power is needed elsewhere in the campaign or, when reinforcement is necessary in order to bolster morale in a given campaign. I would think they would be more reliable in a familiar situation and less likely to thrive in a multi pronged alternating attack situation when outcome and enemy force is unpredictable.
Not as long as the emperor lives. Alien scum are not to be trusted.