Miki. I think I initially picked her because she looks like a young Mayu. On stage she has tonnes of energy and is super energetic. Her over-the-top dancing reminds me of Yuko's. She's a really good idol who pays attention to her fans off-stage and on. On-stage she'll smile at you and give you eye contact if you are supporting her, and at the high touch after the show, she was just really happy to see me as she recognised my support through the performance. However, with Miki, I feel like if I watched variety shows I would hate her, as she seems like she's really really damn annoying on those.
Okada Nana I've never been too keen on, but I will say out of Team 4 she does stand out. As for Kojima Mako, she's so bland I don't ever realise she's actually there. I think this is the key to her popularity though - just being cute and charming but not standing out - so there's nothing to dislike, and people will like her charm like they liked Acchan.