I feel like they are honestly easier to write nice with. With a ballpoint pen, I tend to scribble where as with a fountain pen my writing seems more legible. I also find them more comfortable for longer writing because I don't have to press the pen on the paper. It's more like its gliding across it.

I also like that they are refillable with pretty much any ink I want and that their refills come in glass bottles as opposed to metal or plastic cartridges that are just thrown away when empty. Of course there are plastic ink cartridges for fountain pens, I just don't use them.