I think we are back to requirments again. I prefer to think on along th line of using HTTP protocol. HTTP can be used interactively or batch.
WEB give the impression of person to machine.
HTTP operates directly point to point and thus in general it will perform better in 'real time' applications. SMTP has the advantage when the network is not as reliable, retry can be auto initiated. FTP has the advantage when the file to be transferred is large and the network is not reliable, and retransmission can be resumed from the interrupted point. 1. person fill in the form, EDI message is produced and send to the server via HTTP, the server pass EDI message to the translator, and acknowledgement or reply is returned immediately. 3. customised EDI translator send message to HTTP server directly, server pass EDI message to remote EDI translator, acknowldegement or reply is returned immediately.