@mwichary @mez
I actually found the example by typing "-123" into Firefox's address bar and looking what it came up with

However, Firefox's completion searches history by both URL and title, in any order. If I type "new stargate series", I get both that article and https://reactormag.com/stargate-amazon-mgm-studios/

@mez @mwichary

Off the top of my head...

ID first means the URL can survive truncation of the slug part. Particularly good if you can keep the prefix short.

Slug first means URLs sort in alphabetical order by their slug. Maybe more suitable for small numbers of items, like a blog?

ID first is also marginally easier to construct a URL by hand - you generally don't need to add a fake slug, just end the URL at the ID and it still meets the pattern

Random example of slug-first that happened to be in my history:
- canonical URL: https://www.hollywoodreporter.com/tv/tv-news/stargate-revived-prime-video-new-series-1236431118/
- doesn't work with only ID: https://www.hollywoodreporter.com/tv/tv-news/1236431118/
- works if you know the format and add a fake slug: https://www.hollywoodreporter.com/tv/tv-news/yeehaw-1236431118/