Alright, fine! I will elaborate:
F-Smash is visually different from Mario's, and also functionally different in one way: The sweet-spot is closer to Dr. Mario's fist than his electric blast, unlike Mario who has his fire blast being his sweet-spot. He walks and runs slower than Mario, and doesn't jump as high. His air speed is reduced, but his fall speed was upped. His forward aerial is not a spike, his attacks are generally more powerful, and his nair gets stronger the longer it's out. His sheet also doesn't stall in the air unlike Mario's cape. Super Jump Punch is also a single-hit power move (with no coins) which possess more power at the start of the move. His pills keep their properties from Melee like increased hitstun and a stronger bounce effect. He also has two different moves in his down special and his dair and his Final Smash is visually different.
Lucina's differences include her consistent strength and her slightly shorter size and shorter vertical reach, but she otherwise shares everything (attack speed, movement speed, jump height, air speed, and so on) with Marth. Well, and a different Shield Breaker animation, but that's mostly visual aesthetics. The only ones of these changes that seem to matter in the long run will be her consistent strength (which is the most defining difference between Lucina and Marth) and slightly shorter size and vertical reach which sucks for her since the moveset she's copying was designed around spacing one's attacks, and the character she copied it from not only gets better reach on attacks (which is advantageous for movesets that are meant for spacing) and also has the same attack speed, but is also rewarded for basically taking advantage of what the moveset was designed for, unlike Lucina.
I'm going to guess that every single attack that has a vertical part has worse reach than Marth's on the vertical side, so f-tilt and forward smash among others. Testing her and Marth's attacks on Battlefield with the opponent standing on one of the side platforms allowed me to notice it: Marth was standing further away from the opponent when I finally hit him, while Lucina was definitely closer.