I've used the Aegis line with space marines and imperial guards, and found it utterly boring (because it prevented units form moving out and thereby losing a game-phase) and the quad-gun underperforming (at least against Helldrakes).
Seen as you play Word Bearers, it might be an idea to 'chaosify' some guards into renegades and use a Hydra in an allied detachment, if you are not planning to use a drake yourself.
I cannot tell you anything about the other fortifications, because I haven't used them. I prefer to use the points for more mobile units
What fliers are you expecting to encounter?
How much terrain do you use in your games?
Have you considered Rhinos as mobile bunkers?