Making it clear that I never worked with Racket... Guile was the most ergonomic Scheme I used. Great documentation, "mostly" batteries included, and a while loop macro (the blasphemy, but the convenience!).

The reason I switched was that I wanted to use my small programs on servers, and with Chicken Scheme it was easy to build a statically linked executable. Guile should definitely be packageable as such, if someone versed in C has the patience, but it isn't out of the box and there are no "project templates" out there.

Just my personal opinion: Racket and Gerbil Scheme are the most useful Schemes because of their fairly rich standard libraries. There are other Schemes I like to play with but I don’t do much with.

Sorry for the plug, but I wrote a Racket book last year and I am just now about 20% of the way through a Gerbil Scheme book. I have a luxury: I am retired so I can write on topics that fascinate me, even if I get small audiences.

It's a good plug. I've had an eye on Gerbil for a while, and miss the batteries included aspect of Python when compared to overall Schemes

The standard library can be very practical, if it implements the SRFIs you need. And Guile implements quite a lot of them.