What are some alternatives?
When comparing Cloudu and Cyberduck, you can also consider the following products
Filestash - Filestash is a modern client for FTP, SFTP, S3, WebDAV, Minio,...
FileZilla - FileZilla is an FTP, or file transfer protocol, client. It lets individuals transfer single files or batches to a web server. For many years, FTP was the standard for website design. Read more about FileZilla.
FlowCloud - FlowCloud is online cloud storage GET 120GB FREE!
WinSCP - WinSCP is an open source free SFTP client and FTP client for Windows.
Dropbox - Online Sync and File Sharing
Forklift - The most advanced dual pane file manager and file transfer client for macOS.