Authors of "Legacy of the Force"
Legacy of the Force has three authors, and they all see to present Darth Caedus and Luke Skywalker differently.
Troy Denning presents the duo as their most powerful. In earlier works, Denning gave Jacen Solo all those new, unique abilities, and he also had him do the tutaminis feat against the cruiser fire. For Luke Skywalker, he has him overpowering the likes of UnuThul. The Legacy of the Force is an extension of this, in which he stresses time and time again that they are the main two Force users in the galaxy. Note it was Denning who had Luke Skywalker pin Jacen Solo with a gesture, but also Denning who had them fight in a brutal spectacle. In Invincible, we see Jacen Solo's powers further showcased against Jaina Solo, but he's still completely overshadowed by Luke Skywalker, who is putting him to shame without even being in the same room.
Aaron Allston, on the other hand, downplays the two. Allston suggests that Saba Sebatyne would be a difficult battle for Jacen Solo. He also portrays the gap between Luke Skywalker and Saba Sebatyne as small, with Sebatyne performing significantly better against Solo's assassin droids. There's also a significant inconsistency between his portrayal of the two in Betrayal and Fury. Betrayal has Jacen Solo being capable of one-shotting Lumiya, but is significantly inferior to Luke Skywalker with a blade. In Fury, Jacen Solo is seemingly capable of countering Luke Skywalker's telekinesis, but can only nudge a distracted Saba Sebatyne. All in all, the trend seems to be that the gap between Force-users aren't that large, with Lumiya being the exception and underdog. This is, obviously, inconsistent with the large distinctions between Force-users made by Denning.
Karen Traviss is terrible. The way she writes about the Force and Jedi is inherently biased against them. She consistently downplays not only Jacen Solo, but the entire Jedi Order - Luke Skywalker included. Whereas Denning would have Luke Skywalker being capable of conquering an entire planetary army and Allston at least a small invasion Force, Traviss would likely have a small group of Mandalorians being capable of overwhelming him. After all, it is Traviss who suggests that Jaina Solo's brief Mandalorian training would make her a match for Jacen Solo's five years of extensive Force studying and mastery.