Hilda, because she has a very bold and mature design (The entirety of Gen 5 protags and even Gen 6 X/Y protags are supposed to be young adults. It was great to have them because it looks like Pokémon acknowledged that their audience has grown with them. Then Gen 7 came and they went back to using loli protags and it's been that way since). It makes her look the most competent out of all the female protags. If I were to pin it down, it's due to her ripped shorts that expresses a certain tone of a more mature sexiness that the other female protags lack IMO, coupled with her large boots conveying that she is ready to kick ass and travel the whole world. Topping it all off is her cap. The iconic signature standard to Pokemon Protag trainer cap, donned by Trainer Protags such a Red, Ethan, Hilbert, and Elio. Hilda is the ONLY female protag to wear a cap. That is a bold statement in of itself. And of course her amazing hair, even wearing her cap, you can tell she still takes a lot of care for her hair and grooming her self in general, even when dealing with the everyday responsibilities of being a Pokemon Trainer. Again, it's that mature sexiness that puts her above the rest.

The background behind Hilda's provocative design is because her scenario, Unovan, is based in New York, which makes Hilda a young American woman, they dresses more sexually than her Japanese counterparts. The Game Freak's designs must have been inspired by college girls from campus or upstate NY because she looks more like a Redneck/White Trash woman from the Southern USA (Daisy Dukes, Trucker hat with a pony tail, Tank top/Sleeveless jacket and Combat Boots with Red Laces).