So Marth is for a more thoughtful playstyle, while Lucina is better for the balls-out, in-your-face type. Good to know, thank you.

The overall difference between Marth and Lucina is that Marth has a sweet spot at the tip of his sword unlike Lucina who's attack power is balanced throughout the blade. Lucina's sword also has slightly less range in her attacks than Marth. With Marth, spacing is key in his playstyle as he can output large amounts of damage on an opponent while remaining at safe distance away from them, unlike Lucina where because she lacks that sweet spot on the tip of her sword, has to play aggressively and doesn't really benefit from playing like Marth. Because of Lucina's lack of power, she has to work much harder to rack up damage and get KOs, while Marth can do so much more easily while keeping at a safe distance and dealing more damage overall.