There's a multitude of emulsions available, even after a lot of them have been discontinued. Each one reacts a little differently to light, both in terms of requiring more or less light, but also in terms of reacting in various unique ways to light.
We have reached a new stage with Kodak, and I'm not pleased about it. With prior film discontinuations, Kodak gave advanced warning that a film was going to be discontinued, perhaps with a suggested replacement film. Now, we're faced with films being discontinued without the courtesy of advance warning so we can calibrate our process for a new film or alternatively stock up to complete a project while there's still film to be purchased.