Most of the time I use a pencil or a fountain pen, and while not being perfect or that convenient in general they are when then are functioning as intended they just work. This is not something that is always true for other types of pens.
As I was writing with a gel ink pen more or less exclusively for like a week I discovered that it much more ink flow problems than I remember. Not a big issue most of the time. But I often write some, scribble in the margin while thinking or being bored to death in a meeting. Draw a scare and color it in and stuff like that. The gel ink pen didn't keep up very well at this. Never been a issue with any of my fountain pens.
Same goes with pencil.
It have made me appriciate fountainpens a lot, and realize how great they are if you can accepet their weirdness.