IMO one of the big advantages of Jekyll is that you can extend and modify it to no end, which is a lot harder in Hugo. The choice of language plays a big part here: Ruby just makes this kind of stuff a lot easier than Go.
On my website I do stuff like:
- Run Vim to add syntax highlighting (with :ToHTML).
- Add a tag to include a code example from an external file (much easier to test/run when writing!)
- A tag to list "related posts" based on tag.
- Overwrite the standard date formatting function so I use my own date format, and add a custom number format function which uses a thin space to separate thousands.
- Generate pages for my Go "vanity paths" based on just an Array in a Ruby plugin.
- A tag to include images as base64 inside the page itself.
- Run some regexps on the generated HTML to add/change some things.
- Aside from the .html page, it also generates .txt files for people who prefer this and/or usage on Gopher/Gemini (actually, I removed this as it never worked quite how I wanted, but with a little bit of extra effort it would have, I just couldn't be bothered).
Maybe it's crazy to do some of these things like running Vim, but I like the Vim colour scheme and semantics and it's a lot easier to use this than configuring some library. I wrote much of this years ago and has been working without problems ever since, and it didn't even cost me that much effort.
Either way, my point is: this is a major advantage of Jekyll. Hugo probably has some of this by default, but last time I checked you couldn't even add a custom template function. Once you reach the limits of what you can do with Hugo: you're going to have a hard time. If you hit the limits with Jekyll: no problem, lemme just whip up some Ruby code.
I never hit "random quirks" though, in spite of all my hacky stuff.