Hi Clive-Andrew,
The Gillot 404 you have seen there is blue in colour and current production nibs. The vintage ones were bronze in colour. The general thumbhole is that the quality of the vintage nibs are better than the modern ones.
The Gillot 303 is a very sharp nib and requires a very light hand. They also have been facing quality issues in that you will get some nibs in a lot that are misaligned or just won't write.
The Gillot 404 is also quite fine but does not give as large a swell as the 303.
These are both cheaper nibs and work well once you develop a hand for it.
The Ranga pens are good and if you have a #5 feed and nib on any of them, you can fit out the G nib and make a nice flex pen.
If you haven't got any of them with the #5 and it is still not shipped, email Ranga and ask him to put a couple of feeds in with the pens. Specifically ask for a #5 feed.
http://www.fountainpennetwork.com/forum/topic/282426-rangas-mr-kandan-does-it-again/If the pens are not yet made, and you are interested in this, I can send him a G nib from here and he can fit it out in one of your pens you ordered.
I got a dip pen made from him too
http://www.fountainpennetwork.com/forum/index.php/topic/265884-a-dip-pen-with-a-difference/Both these posts are on another Fountain pen forum.
Happy writing
Prasad