Katarina - HG over Banshee's?

Hello there!

As the new runes hit the Rift, I picked up Kat. There is something that troubles me, though.

When facing an AD mid such as Zed or obnoxious Yasuo, I always go HG - no exceptions. However, I face AP mids sometimes, too, and there's that little thing about the new runes. I can't start with bonus MR the way I used to. This leads to bursty APs such as Fizz or Annie outdamaging me easily, especially early on. I realize HG is a must-have on Kat since it allows for easier dagger/reset access if I can't deal with my opponent quickly enough, however... It doesn't always work against speficic APs. Picking both HG and Banshee pushes me behind with damage, so I don't want to combine both. What are your thoughts? Should I stick to HG even against APs, or is Banshee's a more reliable purchase in those situations? If so - why?

Cheerio.