Bastion vs. Aegis - A Fortification Dilemma

It seems like everyone brings an ADL these days.

With my Chaos Space Marine list utilizing Daemon allies, flyers, and fragile troops which I want to keep off the board I knew I needed a comms relay. The question quickly became to take a bastion or an aegis line to secure myself those sweet, sweet, rerollable reserves.

Aegis Defense Line

If you play 6^th edition Warhammer 40K then you are more than familiar with an aegis line. It is cheap, long, and gets the job (in this case reliable 4+ cover) done. Because my troops are T3 with a 6+ save, 4+ cover literally is a life saver (for whatever life zombies possess). The aegis also serves a key purpose in protecting the havocs in case the deployment zone does not have a ruin or area terrain on a hill. With the short sides of the aegis and the table edge you can ensure they are protected on all sides from flyers. There really is not much to say about the old dependable aegis line.

Bastion

14 armor all around, with a building and battlements, plus several heavy bolters; my own little castle. This fortification caused me to have to lose five zombies to make up for the cost. There were several reasons for why I started playing with the bastion. First was the extra anti-infanty shooting the bolters gave me. At the time I was worried about daemons, and knew I needed all the shots I could get. Second is the perspective it gives the havocs. One squad will have line of sight to the entire table due to their elevation.

Third, was that the bastion was a safe place for a zombie squad to hide. There were two uses. In most objective games the bastion was deployed with its back seven inches from my table edge, with an objective right by the door. This meant that there was blocked line of sight to any unit which was on the objective. The other way was in the relic, and correct me if this is a rule violation, I would put the bastion 11 inches from my table edge with the door facing table center. Because it is in my deployment zone I can put models inside, and so when they disembark they would be several inches further forward than they would have been on the table. This helped to offset the slow speed of zombies in the relic.

One last advantage would be the conversion potential. The idea of a walking fortress (using defiler parts) is quite appealing.

In Comparison

The first big thing to not here is that the bastion can be blown up. In my games with I only had one opponent try to blow it up (succeeding after rending four times on eight attacks). Overall though, I believe its strength, and the other threats I provide keep it safe. You know who else is safe? The people the heavy bolters are targeting. There was one game I played where I only got one hit the entire game with them. The anti-infantry gains from the bastion, even when statistically average or good, are not worth the increased cost. 

The perspective shift given by the bastion was not for my havocs but rather my opponent's shooting priority. When they were on top of the bastion the havocs were the biggest target by my opponent, leading them to be tangibly less durable. The gain in field position for the zombies (outside of the relic) also was inconsequential; any gains made can be compensated through the same objective placement patterns I was using prior to the bastion. Finally, while the conversion would have been cool, I am sure I can come up with something equally awesome for my aegis line.

In conclusion, there is no reason I can see for why I should take a bastion over an aegis defense line when playing with my Chaos Space Marines. Any reasons I missed?