By working via one TCP connection it’s easier to configure it to bypass firewalls, NATs and proxies. In FTP the data channel can cause problems with proper NAT setup.
Again due to one TCP connection, which can be persistent, WebDAV would be a bit faster than FTP when transferring many small files – no need to make a data connection for each file.
GZIP compression is a standard for HTTP but not for FTP (yes, MODE Z is offered in FTP, but it’s not defined in any standard).
HTTP has wide choice of authentication methods which are not defined in FTP. Eg. NTLM and Kerberos authentication is common in HTTP and in FTP it’s hard to get proper support for them unless you write both client and server sides of FTP.
WebDAV supports partial transfers and in FTP partial uploads are not possible (ie. you can’t override a block in the middle of the file).
We’re upgrading our server technology to be faster and more reliable than ever before, and FTP isn’t natively (or easily) supported in the new environment.
WebDAV provides faster speeds for transferring multiple small-sized files — exactly the kind of transfers our merchants make most often.
WebDAV makes it easy to see who last edited a file. This is particularly handy for our Support Ninjas and Partners who help maintain stores.
WebDAV supports file locking, which means only one user at a time can modify a file. Each file is “checked out” so nobody can accidentally overwrite more recent changes.