Both are broadcasting through the markers, but the Brethren Moons have the stronger signal. My theory is that the extra intelligence is because of a war between the Brethren Moons and some unseen species. Also, in Martyr, a hallucination tries to stop someone from turning into a necromorph by entering the 'dead space' mentioned in point 1. Depending on how you look at it, Nicole was trying to aid Isaac. Certain people have hallucinations that advise caution and try to help them resist the marker.So they must have at minimum utilized markers for an energy source, and possibly got the plans from it. How did the aliens on Tau Volantis know how to stop the convergence event by freezing their entire planet? The energy alone required would be more than a resource starved species could handle.You could argue that it was waiting for more biomass, but then why did it not attempt to better it's situation until the marker was removed? Similar to point 1, Marker 3A stopped The Hive Mind from being active just by being near it.It was also in one of the animated movies(Can't remember which one, it took place on the Ishimura I believe), where the hero shelters near the marker since the necromorphs cannot approach.

Markers have 'dead space'(called this in Dead Space: Martyr) that stop the necromorph re-animation.I believe this proves that the markers are amplifying and broadcasting the necromorph signal from the Brethren Moons, but there are other signals trying to stop them as well. In the lore, there are several instances of the markers working against the necromorph invasion and convergence. I will be arguing that the markers are more like radio relays than producers of the necromorph signal directly. Hi fellow CEC employees! I have come to the wonderful realization that the Brethren Moons have been lying to us, and the markers are actually from a 3rd group!

Dead space brethren moons explained