I feel like it's kinda rare for a character to truly win neutral because of better framedata. Falco might sometimes with lasers, but that's iffy too.

Like in the game, slower moves tend to also be bigger. Falcon's nair will lose to Fox's if they both put it out at the same time, but if Falcon inputs his nair earlier, Fox loses that interaction hard.

Probably also depends on MUs. Like Peach dsmash being frame 5 feels much more relevant vs Marth or Sheik than vs a Spacey.

Overall if I had to name two, Sheik and Peach feel like the characters that become whirling vortexes of hitboxes the most often, so if for some reason you want to always have the upper hand exclusively in terms of framedata, you should probably dual-main those two for varying situations.