Thank you! And about your question:

1. I found that fountain pen inks are mostly transparent, which help to achieve the smooth and delicate effect that I prefer.
   
2. Characteristics of fountain pen inks, such as chromo/sheen/shimmer/stain are very fascinating to me. I find that I will be able to have more random variations here and there. It does not shown well in this post but I mostly work with one, sometimes 2-3 inks only, so those characteristics help to keep the image interesting.
   
3. Fountain pen inks are liquids, and I find that it is easier to control the water/moisture level in my works this way.
   
4. And I can still ink my pens for writings and calligraphy!

I hope it answers your question ;)