G-Nib, Sailor Fountain Pen, and Casein

Newly bought a couple of titanium G-nibs from Straits (a local art supply) to test out. Worked really well and better than the steel G-nibs. I used it with a type of Chinese sumi ink that does not bleed on my sketchbook, but the ink is not water-resistant so it dissolved when I was painting with casein. In the middle of drawing the objects on my working desk, I switched to using a Sailor Fude Nib Fountain Pen. Would you be able to tell the difference and where I switch the pens? I don't think I could tell the difference too. Both pens are capable of providing a variety of line weights but the line characteristic is inherent to the artist's style of drawing, which is a result of how the artist holds the pen, and how he draws a line (in regards to direction, pressure and movement of the pen). Every artist should expound on their special way of wielding the pen or the brush, but this could only be achieved by having a good pen mileage.