For those who write often with fountain pens. Other than looks - is there an advantage of a larger nib - say a #6 over a #5? Assume the same nib manufacturer and quality.
I find that it is "smoother" writing with a "6" vs. a "5" nib. Much prefer my script with the larger nib and is just more pleasant to write with.
I now write with a FP exclusively during my day at the office.
In my experience, it's aesthetics (and only the tip of the pen is in contact with the paper anyway!)
A big fat pen with a small nib just looks silly to me. A narrow gauge pen with a huge nib will be difficult to manufacture -- the internal clearance in the cap has to be large enough that the wings don't scrape the walls.
While I agree with Duncan that the "tip" is the only thing in contact with the paper, in a 6MM nib your front section is slightly larger giving you a much better feel and control when using therefore a better writing experience. Also it just looks so much better on the new versions of component sets that are being offered such as the George,Aaron,Panda etc.
LeRoy, For me, they both write the same after the nib has been tuned. However, I like the larger nib. I don't know if it is the looks, the feel or maybe the distance between my thumb/finger and the paper. Sometimes we humans like or dislike things without any real reason other than our personal human nature. My 2 cents.
My thought is the nib size (not tip) is pen body dependent. I have a sterling silver Americana that would look silly with a #6 and of course a Jr Gent or Panda would look silly with a #5 or smaller. My Century Classic from Cross is even smaller then a #5 and I like the way it writes. Put a #5 & #6 side by side and you'll see the #6 is not only much wider but also longer which would give it a different feel as well. I really boils down to trying both and choosing for yourself. I've had ladies with small hands that like a large pen with a #6 and gentlemen with large hands who prefer a slender pen. All about taste...