As a persnickety grammarian, I always prefer proper usage.
Except when faulty sentence structure connects especially well with the target audience. Then, even a sentence fragment will do. This happens when creative copywriters work hard to write in the informal Inside Voice in the head of the target audience. Y’know, like Toys ‘R’ Us. Unspeakably bad English. Works great.
The exception was when Young Isaac was working for an African-American client. “As a minority-owned business, we can never use colloquial, grammatically inaccurate syntax in our advertising,” he said. “Because I’m black, people will presume that I’m uneducated.” Despite his Stanford B.S. and Harvard M.B.A., he had to worry about others’ prejudices. Sadly, I had to agree with his logic.
Woman-owned businesses might worry about the same. What a world.
And, of course, our educational clients at Young Isaac struggle to balance proper usage with relevant language. College kids know when they’re being spoken down to. And they don’t like it. (We help our college clients find that balance.)