No, SFTP and FTPS are for quite different purposes. The sites/servers I access to transfer files are pretty much 50% FTP(S) and 50% SFTP. Some of the FTP sites also support FTPS, but none of the SFTP servers I happen to use support FTP(S).
FTPS is just an extension to FTP protocol, but SFTP is its own protocol which works usually over SSH. So, servers I have access with SSH (shell accounts) can be accessed with SFTP and I can organize my own files in home directory etc. FTP(S) sites are usually more public and "sandboxed" , and the sites I use still allow access without encryption too.
SFTP is handy because you have that by default on any *nix box you have access or set up. It's also much more comfortable protocol, because all access goes through one port and you don't have to fight with data ports and firewalls as with FTP(S). I also have some own servers and media center boxes etc, and it's handy to access them with SFTP and I just won't bother wasting time to setup FTP(S) servers on them.
In any case, hURL documentation tells "hURL supports an incredibly wide range of transfer protocols, e.g. DICT, FILE, FTP, FTPS, Gopher, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP,
SCP,
SFTP, SMB, SMBS, SMTP, SMTPS, Telnet and TFTP." and I didn't find any mentions that if some of these wouldn't be supported on some platforms. Maybe there's something else missing too, but SFTP would interest me atm