I have had some trouble with grammar styles lately. English grammar is complicated, I'll give you that. But because there are so many different style guides that a person can follow, I often find myself debating with editors and other writers about specific rules that vary from one style guide to another. And it's ridiculous because for work purposes there is one style to follow – whatever the boss wants. But there's always room for debate since some rules do change over time.
Most of my work is required to follow AP guidelines. Most of these guidelines are specific to how proper nouns and organization names are capitalized. Not a problem. I was a journalism major at one time and trashed my AP style guide because I used it so often. There are other styles out there, however, that tend to contradict this journalistic style. The rule I often remember between AP and MLA that changes is commas in a series. “Sally, Betty, and Sue” is MLA. “Sally, Betty and Sue” is AP. The last AP-specific job I had to do didn't want this. They wanted to mix MLA styles with AP styles and it was crazy. But again, you do whatever the boss wants, otherwise you won't get paid.
And then if you are really into research writing, you have follow APA. This I have done mainly for speech classes, but it varies a little from MLA, especially in citing sources.
And I'll be completely honest here: I have no idea how all of the styles listed above differ from Chicago or Turabian style. I've never used Chicago before, and I once had to use Turabian for a research paper. I didn't have time to research the style, so I just went ahead and used MLA and I didn't lose points.
My suggestion for the writing world is to pick one style and stick with it. I'm tired of having to know (or pretending to know) five different writing styles, when most of them only differ on source citations.