This is a different world to me... ha, well, it's sci fi... du'uh,
anyways, from the whole graphical feeling, i like the bottom one a lot. It has nice shapy... contrasts and i like the weight of the lines and how you distributed the areas.
from the design, it's hard to tell. I am somehow quite intrigued by the 3rd - because it has some kind of twist in it - a machine becomes a bit more organic and "used by a human", if there are elements that twist in different perspectives. Hard to explain. Maybe that's unintentional or even an unwanted mistakes, but for me, that makes it more interesting : )
yay for uniform but not aerodynamic ship designs for the most part! I love space craft designs, but so often people make designs that would also fly in an atmosphere (which is fine, because some ships would) which seems impractical to me for things like battle cruisers and like gigantic ships. anyway, kudos, great work