There's a bunch of paywalled features of nginx, like healthcheck-based load-balancing, that caddy has out of the box. Caddy also (IIRC) has experimental support for QUIC and has a directory view. There's others too but I'd have to trawl the nginx docs for them and I'm being lazy. The healthcheck-based load-balancing thing is a big deal for us at $WORK because we ended up having to write our own code to handle this instead of use nginx to avoid paying for nginx.