So it is it safe to agree at this point that Ash's Lucario, did in fact, have better development build-up, and focus than Roy's Lucario?
I know Horizons is far from over, but it feels like Roy's Lucario has "completed" its arc having obtained its second Mega, so I think it's safe to evaluate both now.
Ash got his Lucario as a Riolu from an egg, and used it in several battles in early JN leading to the Bea arc arc. It evolved during the Darkest Day finale, then Ash used it regularly against Volkner where it got its first major usage after evolving, than Bea round 3, Raihan, and then the Masters 8. It also had several fights against legendaries like Mewtwo, Articuno, etc. even if it lost them all. Ash got his Mega stone from Korrina's grandfather, although that ep was very underwhelming. It also got to learn to aura sync via Ash's Greninja and learn the giant aura sphere.
Roy's Lucario originally came with no backstory, was just on Roy's team in the timeskip. Then we got its backstory and well...it was kind of nothing special. Then Roy's Lucario started losing most of its battles as a Mega, including to Nemona twice, and several other characters even though it was initially hyped up. Then Mayonnaise gave it a second Mega from Z-A and it did decently into Horizon's first conclusion.
Personality wise...they both feel exactly the same. Just the standard stock stoic Lucario personality,so there's nothing much to say here. Ash's did have some personality as a Riolu though. Do you feel Ash's is better written?