Buggy has the advantage of being a much more established character with future appearances, years of growth, and connections to characters that are popular themselves (Mr. 3, Shanks,etc.) He also has had anime appearances, and the benefit of having had campaigns from past years. Even if all your campaigns are new, chances are a lot of voters from previous years might fondly remember past campaigns/matches.
For Otohime it's a ridiculously tough match. I guess no one said it would be easy to fight against such giant forces … but Otohime did it, and she deserves all the support she can get. Especially since this may be the only year she has a strong chance as she rides the wave of recent events.
Sorry Buggy supporters. I'm on Otohime's side now :P