[Child-of-the-Emperor]

Fulgrim's manipulation of Perturabo was a critical part of his plan to gain Angel Exterminatus, it was his intention from the very beginning - the central element of his plan.

Lorgar's original intention was not to save Angron, it was nothing to do with Angron - it was to remove Guilliman and the XIIIth from the war by creating the Ruinstorm. IIRC it was Horus that demanded that Angron and the World Eaters accompany the Word Bearers to campaign amongst the Five Hundred Worlds. After a while Lorgar realised that Angron was dying and chose to try and save him, but it was never his central objective.

Aside from that we can analyse the character of both Lorgar & Fulgrim. Lorgar, despite his dedication to the Dark Gods, does not seem the person to willingly (or at least readily) betray a brother, friend or ally. Despite his corruption, he still seems to be fighting for what he thinks is right - for the betterment of Mankind (especially as of The First Heretic, although admittedly this seems less so as of Betrayer). Fulgrim, on the other hand, after his depraved corruption would seemingly do anything or betray anyone to achieve his goals.

 

[Child-of-the-Emperor]

I did like the view of Lorgar towards Sanguinus and even Russ... it seemed revealing. But CotE, that was a good analysis. I actually am forced to agree with you, though I must confess I was on the side that thought (maybe I still do... I'm not sure) that Lorgar was trying to save his brother.

I also think that Lorgar was genuinely trying to save Angron. It just so happened that, as gen said, Lorgar's quest to save Angron readily coincided with his primary objective of knocking the Ultramarines out of the war. It was a bonus.

In contrast, Fulgrim's intention to ascend to daemonhood utterly relied on him duping/sacrificing Perturabo.

The two separate examples can't really be compared to be honest.