Characters and seiyuus for me, but it was a tough call because I really love everything about iM@S. Good, bad, and so-bad-it's-good.
The characters are just so funny and relatable and cute and lovable. And the seiyuus really bring them to life. I can't imagine anyone other than Chiaking delivering that "Ara, ara~..." quite like Azusa, or Takane's mysterious, flowing, legato voice being anybody but Harami. I love them all.