What is about the manga that you like more?
The fact that it's more action oriented?
I kinda liked the more political/cloak and daggerness of the anime.
More character development for one. Akira's past is 10 times better in the manga compared to overly done amnesia cliché in the anime.
The other thing I like is Mina's true form design. It pays homage to Witchblade. Not to mention, we see the form quite often in the later volumes (lots of fanservice).
Ah, I see.
I think they did that cause they probably knew they weren't gonna get a second season.
(just speculation on my part)
And as for adult Mina...
It all goes back to fan service.
( I kid, I think she's more bad @ss like that too.)