Norfleet,
I've only a very light knowledge of AE. Maybe they're more effective in early expansion (but even so SG is not that bad at it).
However what struck me is that the SG units are efficient throughout the game and whatever the enemies are , whereas Soulless and Longdead hordes are pretty weak and useless as soon as big units appear.
I'd try AE soon in a new game to have a better understanding of them
