>>531936807
I assume you mean from a pure design/artwork perspective

For me, it's Swimsuit Kirino, who is so fucking cute, so goddamg fucking cute. Look at her, holy shit

However, if I'm being totally totally objective...hmmmmm
That's where it gets tough

My personal favorites
Kirino, Chise, Izuna, Fubuki, Hiyori, Hoshino, Koharu, Shizuko, Seia
No particular order other that #1 Kirino

I think the objective best swimsuits are these:
Hoshino, Koharu, Seia. I honestly think Seia's swimsuit ourable but also arousing, and maybe, just maybe, Hoshino is objectively the best. I feel like this is tough to say with certainty.

Honorable mention to Hiyori who in my opinion has the most arousing swimsuit alt.