I think she has less holes than Batman. I guess the obvious thing to point out is that Batman has better zoning, and that's fair, but she does better in the footsie game, has better range on her normals, 50/50's, better pressure (pretty much every Batman string has holes), frame traps for days, better wake-ups, a better corner game and a better oki game. I also think she's better defensively and has a better anti air. Batman is way too reliant on his trait by comparison too.
I'm actually in the clan that thinks WoWo is underrated. Looking at her, while she's "honest" in the sense that she just plays the game and doesn't have pure bullshit or an overpowered tool that you have to respect, she's extremely well-rounded (which is generally the argument in favor of Batman), only less flawed. I say she's a solid lower half of the top 10 character who can compete with most of the cast.