Ceph is quite expensive in terms of resource usage, but it is robust and battle-tested. RustFS is very new, very much a work in progress[1], and will probably eat your data.
If you're looking for something that won't eat your data in edge cases, Ceph (and perhaps Garage) are your only options.
I recently learned that Ceph also has an object store and have been playing around with microceph. Ceph also is more flexible than garage in terms of aggregating differently sized disks. Since it's also already integrated in Proxmox and has over a decade of enterprise deployments, that's my top contender at the moment. I'm just not sure about the level of S3 API compatibility.
Any opinions on Ceph vs RustFS?