Justin's initial attraction to Wisteria is for almost the same reason that Nik was initially unimpressed by her: she has a slender, boyish build. Nik likes his women very feminine and his men very masculine, while insofar as Justin has a type, it's "tall, slim, masculine". Justin also admires assertiveness, composure, and confidence, and Wisteria's demeanor reflects all of that (basically by default -- since almost no one can read her muted body language, they interpret her as being calm and composed all the time).

But yeah, Justin likes Wisteria because she understands business at least as well as he does and it's good to talk to an equal. He doesn't find many people his age that he can say that about.