Sorry, but I just wanted to address this.
Piano roll is far more intuitive than staff notation. It's so much easier to visualize intervals and relationships between notes because, well, they're staring you in the face. I can see that a chord is minor by just looking at it, instead of reading what the notes actually are and figuring out where they fall in the diatonic scale (I realize of course that to a trained person, the time saved is a matter of a few seconds, but still).
By the same token, when you're composing, you're less likely to confine yourself to the diatonic scale. I hate the term accidental, because it makes it seem like you wrote something you weren't supposed to write. Music can sound a lot more interesting when you branch out from just the 8 notes in a scale.