In the early days, people were saying that the fact that Lucina lacking a sweetspot on her sword like her idol Marth could provide her with an advantage. Now we know that Marth is better overall, but is there a way to take advantage of the even damage throughout Lucina's blade (i.e. play in a way that wouldn't be so effective if done with Marth himself)?
I do believe that since her blade is balanced, alot of the setups and combos I've written on work slightly better in her favor for racking damage up. Like the same DB Up B setup used by Lucina would not stuff up as easily as Marth who would need to be mindful of where he hits the target and for what results he wants. Marth is more likely to kill faster than rack up lots of damage, so it is a choice of priority really. Both of them can do what the other does relatively the same in the end, but Marth does kill slightly faster, but at the risk of placing himself in danger at points if he messes up.
The singular knockback, regardless of where you hit with the sword, does help a bit with knowing exactly where your opponent will go and you can take advantage of it. Others on the post here also stated her better USmash, as well as her application with the SB. The way she swings her SB in particular is aimed higher than Marth's, and can potentially be used to target opponents above her easier than Marth can.
I'm trying to be very careful how I word all this, given what has happened in the past ^^" But hopefully this helps.
Are there players who usually try to avoid tippers from opposing Marths? If so, I can imagine Lucina would be a good choice in those situations.
I am actually a Marth that avoids tippers at points so I can rack up the damage faster via all the setups/combos I go for. But I like the challenge of having to be consious of how I space, and I align myself with Marth more than with Lucina really. But Lucina does make it a bit easier to go for some of those setups/combos, so I give it to her for that as her main advantage