One option that might be overlooked is to *omit* the particle, as opposed to choosing "は" or "が". In this case, it would sound much closer to "は" than "が".

Personally, I would go with this third option, in most cases.

Nonetheless, I concur that [context really is important when discussing Japanese](https://japanese.stackexchange.com/a/30795/11830). There are cases when one would sound correct, and the other incorrect and vice versa.

> In what situations would you use [the former] in?

When the subject is made clear to be someone other than the listener.