We don't really know their personalities so I will stick to designs.
Black Maria, probably, is my favourite right now. I like how her visuals are congruent with her size (long pipe, long horns, long locks of hair...), and I love the hyperbolic resource of using blades as hair sticks and how the sinuosity of her horns rhymes with that of her locks.
I've always preferred pretimeskip X Drake. The sharpness conveyed by his pointy bicorn in conjuntion with his prominent chin provided a profile that worked great with the rest of his aesthetics and concept (the aggressivity of an allosaurus, the X theme, etc.). My big problem with his current looks mainly relies on his zoan transformations: Oda is obviously playing with the spiky hair to merge it with the allosaurus dorsal protuberances, but I don't think he takes full advantage of it and his hybrid is especially horrendous in my opinion (even more when collored)
Ulti has no design. She's just a girl with a mask and generic horns that don't interact in any apparent way with the whole. Her personality is the most interesting to me, which just saddens even more how boring her looks are.
Who's who is okay, but I need to see his torso better because it is the most interesting part of his body, especially considering that it seems to be altered in some way that may matches his mask (because of the whole eyes thematic).
Same for Sasaki too, he's okay and looks good, but I don't really find him that stimulating but, to be fair, there's some nice fluency in his aesthetics that please the eye (both fangs and horns pointing up, the front of his cap fitting with the horns, the dark shapes on his clothes with as much movement as his mane...). So basically everything works but I don't think there's anything too smart or conceptually attractive like said blades as hair sticks in Black Maria.
Finally, my problem with human Page One is that I literally can't identify the character we used to know in that guy. Suddenly Oda is playing with the visual contrast of black versus white that was nowhere to be seen in previous depictions (obviouly he's stressing the asymmetry coming from the half-shaven head, but it just feels unnatural). This new Page One now uses a mask, shoes, a horned hat, a shirt and cape... Where is the Page One we knew, exactly? That who walked barefoot, with his chest open, properly showing his rebellious haircut and jaws? Either the guy was traumatized by Sanji or something doesn't add up.