At my old college, there was a "confession tree" where people wrote things on their mind on a piece of paper and stuck it on a tree. Aside from generic greetings and a cute drawing or two, the tree was almost empty. That is, until someone posted "Yukiko is best girl". I responded with an "Actually it's Chie," thinking it would end there; I was just glad that there was a fellow geek on campus who knew about Persona. However, the next day, someone else wrote "Wrong, Rise is best girl." Then, I responded with "Calm down ladies, we all know Naoto is actually best girl."
It kept going until someone eventually said Kanji is best girl. Then the tree was filled with people agreeing that Kanji was indeed best girl. Then there was Kanji fan art posted all over the tree (my favorite was a stick figure one with his jacket and chair). By the end of the month, there was a second Kanji tree.
I saved pictures of one of the trees and posted it online elsewhere, but it was a few years back. The moral of the story is that Kanji is best girl (when it comes to P4). Even Joker's English voice actor has stated it in interviews, I kid you not.
With that being said, I romanced Kawakami (she's so cool) in P5, but Tae and Ann are equally awesome in different ways (and honorable mention goes to Sae). Granted, I'm a grown woman who mostly cares about the storylines/how relatable the characters are/what I think Joker would like/who wears the cutest outfits, IMO. Gameplay perks played a small factor in my decisions as well.
Regardless, support who you want for w/e reason (they're all cool), but Yusuke is best girl, and I hope that one day he's the de facto best girl for P5, much like Kanji is for P4 (and the orbal bike for Trails of Cold Steel, for those of you who get that reference).
More on topic, I'm not as impatient as I was earlier this month. When Joker is out, he's out. It's happening sooner rather than later, and whenever it happens, it'll be fantastic.