I tested around 100 pens rather thoroughly a few years back, and there were two rather clear winners in terms of writing comfort and writing result:
Cross (*)
Lamy Persona
The Lamy was a rather odd contender, since Lamy is most known for pens at the other end of the spectrum, but this one pen was a true beauty, with titanium body and 18k gold nib and parts.
The Cross (* = I do unfortunately not remember the precise Cross model now) was somewhat thinner, but had an exquisitely fluid nib.
I ended up buying the Lamy, since thickness counts more to writing comfort for me than does the nib, but if I were to construct my own pen, it would be a Lamy with a Cross nib.
Other pens: Many other pens, Montblanc prominently among them, were very pretty
looking but rather poor as writing instruments. Many of them were too thin, too tapered or too slippery at the grip point to give control of the pen without having to use force. The Lamy, in contrast, was perfect in this regard; it lets you write well and controlled with barely any gripping force.
I must give kudos to the seller, Andvord in Oslo, Norway, for letting me spend so many hours testing so many pens, and testing many over and over again until I had it narrowed down. They even gave me a free extra nib when I couldn't decide between fine and medium, just for the joy of the pen afficionado.
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