I think the first one is better. What's the purpose of having all the text crammed in a thin column in the middle of the page anyway? If I'm reading the page on a wide screen, let me use all of the motherfucking screen.
I have posted a link to a research paper in a different comment, however it is generally accepted that 50-70 CPL (characters per line) is optimal for reading. Fast readers preferring shorter lines.
Layout wise this is why newspapers arrange their text in columns and books also generally comply with this restriction.
I agree "HN is excellent" you only need to change the "85%" on the main table to your preference, in my case "70ch" in your case to "100%".
I do wonder how much you need UW for coding, in my experience without the IDE borders and decorations usually the code will end around halfway on my screen.
When I'm using my UW daily screen I usually dock two windows side by side. and didn't find that restricting. But I am also nostalgic for the 4:3 days from time to time.
Eyeball muscle speed limits how fast you can read or, well; at least for me). My eyes simply can't go left and right as fast as I can read, plus keeping track of which line I'm on is extra overhead. YMMV.
Interesting comparison in the context of the top rated discussion about setting width. I'm with @kmoser. The original actually looks better--to me--and I like that I can manage it.
I love these websites as they highlight not only the complexity of modern web design but also that the web is made for writing content. There are so many variations on this "motherfuckingwebsite" concept with a lot of different opinions that I would recommend everyone interested in webdesign to google that term and read through a bunch of them.
https://motherfuckingwebsite.com/
and
http://bettermotherfuckingwebsite.com/