As far as I know there are currently three races using troops and capturing planets (correct me, if I am wrong): The Aquilaeian (AI by Master Belisarius), the Orks(AI by Atraikius) and the Vikings(AI by myself). I suggest that get all three and find out yourself which one does it the best
. I am not sure myself, yet, but my view is biased anyway, since I am doing the Viking AI. If you do this, please let us know what you think.
Have fun,
Rollo