(The navy blue trains with yellow 'noses' are high-speed commuter trains, the dark blue, gold and white ones are the high-speed trains to France, the plain white ones are normal-speed commuter trains to London.)
I think the continuously welded rails are the biggest improvement, as they remove most of the "clackety-clack". Instead you get the "hiss", but that's only noticeable from really close.
https://www.youtube.com/watch?v=7-wyR316550
(The navy blue trains with yellow 'noses' are high-speed commuter trains, the dark blue, gold and white ones are the high-speed trains to France, the plain white ones are normal-speed commuter trains to London.)
I think the continuously welded rails are the biggest improvement, as they remove most of the "clackety-clack". Instead you get the "hiss", but that's only noticeable from really close.