I like their music style, their MVs, the messages behind their lyrics, and yes, the persona the members portray. Stray Kids seem genuine most of the time. I like that all of them are artists. For example, Hyunjin is my Bias. Not only bc I like his dance style and his voice, but I also like the paintings he creates and the lyrics he writes. In a way, he is similar to me (at least his idol persona is). And ofc, he is visually appealing to me.
I usually don't like Boygroups but I just love Stray Kids. I like (almost) everything abt them. They are captivating. Every member seems interesting. I like the way they talk, the way they sing, the way they dance etc.
NewJeans is my female ult group. Not only because I like their music tho. I just feel like- ugh I hate to admit it bc it's delulu but I feel like I can relate to some of the members. I also like the image that they portray. They made my summer 2022 the most memorable one ever, their debut changed my life. They helped me get rid of writers block. Everything abt them is unique. I can relate to almost every single lyric they sing. I love their Music Videos.
you mentioned the persona they portray but isn't that just their personalities??? lol or at least the personalities they show on camera...
since for other groups their "personas" didn't attract you (which again is fine - perfectly valid) but doesn't that just mean that that group doesn't have the group chemistry/personalities to attract you???
you also mentioned music style a lot (for both SKZ and NJ) which I guess is part and parcel of why you stan a group and why a group becomes your ult
then the question becomes - what is different in your opinion between a group that is your ult vs one you merely stan vs one you are merely a fan of vs casual listener (or is there a difference in your opinion???)